diff --git a/csharp/ql/lib/change-notes/2026-01-06-null-conditional-assignments.md b/csharp/ql/lib/change-notes/2026-01-06-null-conditional-assignments.md
new file mode 100644
index 000000000000..e9c5a94478a6
--- /dev/null
+++ b/csharp/ql/lib/change-notes/2026-01-06-null-conditional-assignments.md
@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* The `MaybeNullExpr` class now takes null-conditional access (such as `?.` and `?[]`) into account when modeling potential null values.
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
index 6a211e71f456..756fd6a4e3a0 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll
@@ -43,6 +43,12 @@ private Expr maybeNullExpr(Expr reason) {
     )
   or
   result.(NullCoalescingExpr).getRightOperand() = maybeNullExpr(reason)
+  or
+  result =
+    any(QualifiableExpr qe |
+      qe.isConditional() and
+      qe.getQualifier() = maybeNullExpr(reason)
+    )
 }
 
 /** An expression that may be `null`. */
diff --git a/csharp/ql/test/library-tests/nullconditional/NullConditional.cs b/csharp/ql/test/library-tests/nullconditional/NullConditional.cs
new file mode 100644
index 000000000000..04392fb4e626
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/NullConditional.cs
@@ -0,0 +1,32 @@
+using System;
+
+public class C
+{
+    public int Field;
+
+    public string Property { get; set; } = "";
+
+    public void M(C c, int[] numbers, bool b)
+    {
+        // Get values.
+        var fieldValue = c?.Field;
+        var propertyValue = c?.Property;
+        var n = numbers?[0];
+
+        // Set values
+        c?.Field = 42;
+        c?.Property = "Hello";
+        numbers?[0] = 7;
+
+        // Set values using operators
+        c?.Field -= 1;
+        c?.Property += " World";
+
+        // Using the return of an assignment
+        var x = c?.Field = 10;
+
+        // Using in a conditional expression
+        int? maybenull = 0;
+        maybenull = (b ? c : null)?.Field;
+    }
+}
diff --git a/csharp/ql/test/library-tests/nullconditional/maybenull.expected b/csharp/ql/test/library-tests/nullconditional/maybenull.expected
new file mode 100644
index 000000000000..06c5c376b8e6
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/maybenull.expected
@@ -0,0 +1,4 @@
+| NullConditional.cs:30:9:30:41 | ... = ... |
+| NullConditional.cs:30:21:30:41 | access to field Field |
+| NullConditional.cs:30:22:30:33 | ... ? ... : ... |
+| NullConditional.cs:30:30:30:33 | null |
diff --git a/csharp/ql/test/library-tests/nullconditional/maybenull.ql b/csharp/ql/test/library-tests/nullconditional/maybenull.ql
new file mode 100644
index 000000000000..a11fd2a9151c
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/maybenull.ql
@@ -0,0 +1,6 @@
+import csharp
+import semmle.code.csharp.dataflow.Nullness
+
+from MaybeNullExpr mne
+where mne.getFile().getBaseName() = "NullConditional.cs"
+select mne
diff --git a/csharp/ql/test/library-tests/nullconditional/nullconditional.expected b/csharp/ql/test/library-tests/nullconditional/nullconditional.expected
new file mode 100644
index 000000000000..80d51ab9361d
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/nullconditional.expected
@@ -0,0 +1,12 @@
+| NullConditional.cs:12:26:12:33 | access to field Field |
+| NullConditional.cs:13:29:13:39 | access to property Property |
+| NullConditional.cs:14:17:14:27 | access to array element |
+| NullConditional.cs:17:9:17:16 | access to field Field |
+| NullConditional.cs:18:9:18:19 | access to property Property |
+| NullConditional.cs:19:9:19:19 | access to array element |
+| NullConditional.cs:22:9:22:16 | access to field Field |
+| NullConditional.cs:22:9:22:16 | access to field Field |
+| NullConditional.cs:23:9:23:19 | access to property Property |
+| NullConditional.cs:23:9:23:19 | access to property Property |
+| NullConditional.cs:26:17:26:24 | access to field Field |
+| NullConditional.cs:30:21:30:41 | access to field Field |
diff --git a/csharp/ql/test/library-tests/nullconditional/nullconditional.ql b/csharp/ql/test/library-tests/nullconditional/nullconditional.ql
new file mode 100644
index 000000000000..77735091f79f
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/nullconditional.ql
@@ -0,0 +1,5 @@
+import csharp
+
+from QualifiableExpr e
+where e.isConditional()
+select e
diff --git a/csharp/ql/test/library-tests/nullconditional/options b/csharp/ql/test/library-tests/nullconditional/options
new file mode 100644
index 000000000000..77b22963f5c8
--- /dev/null
+++ b/csharp/ql/test/library-tests/nullconditional/options
@@ -0,0 +1,2 @@
+semmle-extractor-options: /nostdlib /noconfig
+semmle-extractor-options: --load-sources-from-project:${testdir}/../../resources/stubs/_frameworks/Microsoft.NETCore.App/Microsoft.NETCore.App.csproj