diff --git a/docs/changelog/100656.yaml b/docs/changelog/100656.yaml
new file mode 100644
index 0000000000000..1ee9a2ad0e47a
--- /dev/null
+++ b/docs/changelog/100656.yaml
@@ -0,0 +1,6 @@
+pr: 100656
+summary: "ESQL: fix non-null value being returned for unsupported data types in `ValueSources`"
+area: ES|QL
+type: bug
+issues:
+ - 100048
diff --git a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/ValueSources.java b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/ValueSources.java
index e5ce5436990b7..29a539b1e068e 100644
--- a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/ValueSources.java
+++ b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/lucene/ValueSources.java
@@ -69,6 +69,18 @@ public static List<ValueSourceInfo> sources(
                 sources.add(new ValueSourceInfo(new NullValueSourceType(), new NullValueSource(), elementType, ctx.getIndexReader()));
                 continue; // the field does not exist in this context
             }
+            if (asUnsupportedSource) {
+                sources.add(
+                    new ValueSourceInfo(
+                        new UnsupportedValueSourceType(fieldType.typeName()),
+                        new UnsupportedValueSource(null),
+                        elementType,
+                        ctx.getIndexReader()
+                    )
+                );
+                HeaderWarning.addWarning("Field [{}] cannot be retrieved, it is unsupported or not indexed; returning null", fieldName);
+                continue;
+            }
 
             if (fieldType.hasDocValues() == false) {
                 // MatchOnlyTextFieldMapper class lives in the mapper-extras module. We use string equality
@@ -99,19 +111,7 @@ public static List<ValueSourceInfo> sources(
             var fieldContext = new FieldContext(fieldName, fieldData, fieldType);
             var vsType = fieldData.getValuesSourceType();
             var vs = vsType.getField(fieldContext, null);
-
-            if (asUnsupportedSource) {
-                sources.add(
-                    new ValueSourceInfo(
-                        new UnsupportedValueSourceType(fieldType.typeName()),
-                        new UnsupportedValueSource(vs),
-                        elementType,
-                        ctx.getIndexReader()
-                    )
-                );
-            } else {
-                sources.add(new ValueSourceInfo(vsType, vs, elementType, ctx.getIndexReader()));
-            }
+            sources.add(new ValueSourceInfo(vsType, vs, elementType, ctx.getIndexReader()));
         }
 
         return sources;
diff --git a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/DefaultSortableTopNEncoder.java b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/DefaultSortableTopNEncoder.java
index 8634d87e2932f..6ccde6b76ce13 100644
--- a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/DefaultSortableTopNEncoder.java
+++ b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/DefaultSortableTopNEncoder.java
@@ -23,7 +23,7 @@ public BytesRef decodeBytesRef(BytesRef bytes, BytesRef scratch) {
 
     @Override
     public String toString() {
-        return "DefaultUnsortable";
+        return "DefaultSortable";
     }
 
     @Override
diff --git a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/TopNEncoder.java b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/TopNEncoder.java
index 2d8f2666ff2f2..f1fb7cb7736c5 100644
--- a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/TopNEncoder.java
+++ b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/TopNEncoder.java
@@ -41,6 +41,11 @@ public interface TopNEncoder {
      */
     VersionTopNEncoder VERSION = new VersionTopNEncoder();
 
+    /**
+     * Placeholder encoder for unsupported data types.
+     */
+    UnsupportedTypesTopNEncoder UNSUPPORTED = new UnsupportedTypesTopNEncoder();
+
     void encodeLong(long value, BreakingBytesRefBuilder bytesRefBuilder);
 
     long decodeLong(BytesRef bytes);
diff --git a/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/UnsupportedTypesTopNEncoder.java b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/UnsupportedTypesTopNEncoder.java
new file mode 100644
index 0000000000000..d80d70970409e
--- /dev/null
+++ b/x-pack/plugin/esql/compute/src/main/java/org/elasticsearch/compute/operator/topn/UnsupportedTypesTopNEncoder.java
@@ -0,0 +1,45 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.compute.operator.topn;
+
+import org.apache.lucene.util.BytesRef;
+import org.elasticsearch.compute.operator.BreakingBytesRefBuilder;
+
+/**
+ * TopNEncoder for data types that are unsupported. This is just a placeholder class, reaching the encode/decode methods here is a bug.
+ *
+ * While this class is needed to build the TopNOperator value and key extractors infrastructure, encoding/decoding is needed
+ * when actually sorting on a field (which shouldn't be possible for unsupported data types) using key extractors, or when encoding/decoding
+ * unsupported data types fields values (which should always be "null" by convention) using value extractors.
+ */
+class UnsupportedTypesTopNEncoder extends SortableTopNEncoder {
+    @Override
+    public int encodeBytesRef(BytesRef value, BreakingBytesRefBuilder bytesRefBuilder) {
+        throw new UnsupportedOperationException("Encountered a bug; trying to encode an unsupported data type value for TopN");
+    }
+
+    @Override
+    public BytesRef decodeBytesRef(BytesRef bytes, BytesRef scratch) {
+        throw new UnsupportedOperationException("Encountered a bug; trying to decode an unsupported data type value for TopN");
+    }
+
+    @Override
+    public String toString() {
+        return "UnsupportedTypesTopNEncoder";
+    }
+
+    @Override
+    public TopNEncoder toSortable() {
+        return this;
+    }
+
+    @Override
+    public TopNEncoder toUnsortable() {
+        return this;
+    }
+}
diff --git a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_tsdb.yml b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_tsdb.yml
index 14ae1ff98d8ad..895a1718b2cbc 100644
--- a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_tsdb.yml
+++ b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_tsdb.yml
@@ -106,6 +106,8 @@ setup:
 ---
 load everything:
   - do:
+      allowed_warnings_regex:
+        - "Field \\[.*\\] cannot be retrieved, it is unsupported or not indexed; returning null"
       esql.query:
         body:
           query: 'from test'
@@ -156,6 +158,8 @@ filter on counter:
 ---
 from doc with aggregate_metric_double:
   - do:
+      allowed_warnings_regex:
+        - "Field \\[.*\\] cannot be retrieved, it is unsupported or not indexed; returning null"
       esql.query:
         body:
           query: 'from test2'
@@ -183,6 +187,8 @@ stats on aggregate_metric_double:
 ---
 from index pattern unsupported counter:
   - do:
+      allowed_warnings_regex:
+        - "Field \\[.*\\] cannot be retrieved, it is unsupported or not indexed; returning null"
       esql.query:
         body:
           query: 'FROM test*'
diff --git a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_unsupported_types.yml b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_unsupported_types.yml
index 44af9559598ab..ad0c7b516fde1 100644
--- a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_unsupported_types.yml
+++ b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/40_unsupported_types.yml
@@ -263,3 +263,96 @@ unsupported:
   - match: { columns.0.name: shape }
   - match: { columns.0.type: unsupported }
   - length: { values: 0 }
+
+---
+unsupported with sort:
+  - do:
+      allowed_warnings_regex:
+        - "Field \\[.*\\] cannot be retrieved, it is unsupported or not indexed; returning null"
+      esql.query:
+        body:
+          query: 'from test | sort some_doc.bar'
+
+  - match: { columns.0.name: aggregate_metric_double }
+  - match: { columns.0.type: unsupported }
+  - match: { columns.1.name: binary }
+  - match: { columns.1.type: unsupported }
+  - match: { columns.2.name: completion }
+  - match: { columns.2.type: unsupported }
+  - match: { columns.3.name: date_nanos }
+  - match: { columns.3.type: unsupported }
+  - match: { columns.4.name: date_range }
+  - match: { columns.4.type: unsupported }
+  - match: { columns.5.name: dense_vector }
+  - match: { columns.5.type: unsupported }
+  - match: { columns.6.name: double_range }
+  - match: { columns.6.type: unsupported }
+  - match: { columns.7.name: float_range }
+  - match: { columns.7.type: unsupported }
+  - match: { columns.8.name: geo_point }
+  - match: { columns.8.type: unsupported }
+  - match: { columns.9.name: geo_point_alias }
+  - match: { columns.9.type: unsupported }
+  - match: { columns.10.name: histogram }
+  - match: { columns.10.type: unsupported }
+  - match: { columns.11.name: integer_range }
+  - match: { columns.11.type: unsupported }
+  - match: { columns.12.name: ip_range }
+  - match: { columns.12.type: unsupported }
+  - match: { columns.13.name: long_range }
+  - match: { columns.13.type: unsupported }
+  - match: { columns.14.name: match_only_text }
+  - match: { columns.14.type: text }
+  - match: { columns.15.name: name }
+  - match: { columns.15.type: keyword }
+  - match: { columns.16.name: rank_feature }
+  - match: { columns.16.type: unsupported }
+  - match: { columns.17.name: rank_features }
+  - match: { columns.17.type: unsupported }
+  - match: { columns.18.name: search_as_you_type }
+  - match: { columns.18.type: unsupported }
+  - match: { columns.19.name: search_as_you_type._2gram }
+  - match: { columns.19.type: unsupported }
+  - match: { columns.20.name: search_as_you_type._3gram }
+  - match: { columns.20.type: unsupported }
+  - match: { columns.21.name: search_as_you_type._index_prefix }
+  - match: { columns.21.type: unsupported }
+  - match: { columns.22.name: shape }
+  - match: { columns.22.type: unsupported }
+  - match: { columns.23.name: some_doc.bar }
+  - match: { columns.23.type: long }
+  - match: { columns.24.name: some_doc.foo }
+  - match: { columns.24.type: keyword }
+  - match: { columns.25.name: text }
+  - match: { columns.25.type: text }
+  - match: { columns.26.name: token_count }
+  - match: { columns.26.type: integer }
+
+  - length: { values: 1 }
+  - match: { values.0.0: null }
+  - match: { values.0.1: null }
+  - match: { values.0.2: null }
+  - match: { values.0.3: null }
+  - match: { values.0.4: null }
+  - match: { values.0.5: null }
+  - match: { values.0.6: null }
+  - match: { values.0.7: null }
+  - match: { values.0.8: null }
+  - match: { values.0.9: null }
+  - match: { values.0.10: null }
+  - match: { values.0.11: null }
+  - match: { values.0.12: null }
+  - match: { values.0.13: null }
+  - match: { values.0.14: "foo bar baz" }
+  - match: { values.0.15: Alice }
+  - match: { values.0.16: null }
+  - match: { values.0.17: null }
+  - match: { values.0.18: null }
+  - match: { values.0.19: null }
+  - match: { values.0.20: null }
+  - match: { values.0.21: null }
+  - match: { values.0.22: null }
+  - match: { values.0.23: 12 }
+  - match: { values.0.24: xy }
+  - match: { values.0.25: "foo bar" }
+  - match: { values.0.26: 3 }
diff --git a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/50_index_patterns.yml b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/50_index_patterns.yml
index 280a32aa10cd3..ff327b2592c88 100644
--- a/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/50_index_patterns.yml
+++ b/x-pack/plugin/esql/qa/server/single-node/src/yamlRestTest/resources/rest-api-spec/test/50_index_patterns.yml
@@ -267,6 +267,8 @@ disjoint_mappings:
 
 ---
 same_name_different_type:
+  - skip:
+      features: allowed_warnings_regex
   - do:
       indices.create:
         index: test1
@@ -307,6 +309,8 @@ same_name_different_type:
           - { "message": 2 }
 
   - do:
+      allowed_warnings_regex:
+        - "Field \\[.*\\] cannot be retrieved, it is unsupported or not indexed; returning null"
       esql.query:
         body:
           query: 'from test1,test2  '
diff --git a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/LocalExecutionPlanner.java b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/LocalExecutionPlanner.java
index 1c26de4a599f5..b86072e1b6da0 100644
--- a/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/LocalExecutionPlanner.java
+++ b/x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/planner/LocalExecutionPlanner.java
@@ -380,6 +380,8 @@ private PhysicalOperation planTopN(TopNExec topNExec, LocalExecutionPlannerConte
                 case "version" -> TopNEncoder.VERSION;
                 case "boolean", "null", "byte", "short", "integer", "long", "double", "float", "half_float", "datetime", "date_period",
                     "time_duration", "object", "nested", "scaled_float", "unsigned_long", "_doc" -> TopNEncoder.DEFAULT_SORTABLE;
+                // unsupported fields are encoded as BytesRef, we'll use the same encoder; all values should be null at this point
+                case "unsupported" -> TopNEncoder.UNSUPPORTED;
                 default -> throw new EsqlIllegalArgumentException("No TopN sorting encoder for type " + inverse.get(channel).type());
             };
         }