diff --git a/src/services/navigationBar.ts b/src/services/navigationBar.ts
index 2f928f52c7b62..b4c7c5a2c24c1 100644
--- a/src/services/navigationBar.ts
+++ b/src/services/navigationBar.ts
@@ -133,7 +133,7 @@ namespace ts.NavigationBar {
     /** Call after calling `startNode` and adding children to it. */
     function endNode(): void {
         if (parent.children) {
-            mergeChildren(parent.children);
+            mergeChildren(parent.children, parent);
             sortChildren(parent.children);
         }
         parent = parentsStack.pop()!;
@@ -304,7 +304,7 @@ namespace ts.NavigationBar {
     }
 
     /** Merge declarations of the same kind. */
-    function mergeChildren(children: NavigationBarNode[]): void {
+    function mergeChildren(children: NavigationBarNode[], node: NavigationBarNode): void {
         const nameToItems = createMap<NavigationBarNode | NavigationBarNode[]>();
         filterMutate(children, child => {
             const declName = getNameOfDeclaration(<Declaration>child.node);
@@ -322,7 +322,7 @@ namespace ts.NavigationBar {
 
             if (itemsWithSameName instanceof Array) {
                 for (const itemWithSameName of itemsWithSameName) {
-                    if (tryMerge(itemWithSameName, child)) {
+                    if (tryMerge(itemWithSameName, child, node)) {
                         return false;
                     }
                 }
@@ -331,7 +331,7 @@ namespace ts.NavigationBar {
             }
             else {
                 const itemWithSameName = itemsWithSameName;
-                if (tryMerge(itemWithSameName, child)) {
+                if (tryMerge(itemWithSameName, child, node)) {
                     return false;
                 }
                 nameToItems.set(name, [itemWithSameName, child]);
@@ -340,8 +340,8 @@ namespace ts.NavigationBar {
         });
     }
 
-    function tryMerge(a: NavigationBarNode, b: NavigationBarNode): boolean {
-        if (shouldReallyMerge(a.node, b.node)) {
+    function tryMerge(a: NavigationBarNode, b: NavigationBarNode, parent: NavigationBarNode): boolean {
+        if (shouldReallyMerge(a.node, b.node, parent)) {
             merge(a, b);
             return true;
         }
@@ -349,8 +349,8 @@ namespace ts.NavigationBar {
     }
 
     /** a and b have the same name, but they may not be mergeable. */
-    function shouldReallyMerge(a: Node, b: Node): boolean {
-        if (a.kind !== b.kind) {
+    function shouldReallyMerge(a: Node, b: Node, parent: NavigationBarNode): boolean {
+        if (a.kind !== b.kind || a.parent !== b.parent && !(isOwnChild(a, parent) && isOwnChild(b, parent))) {
             return false;
         }
         switch (a.kind) {
@@ -366,6 +366,13 @@ namespace ts.NavigationBar {
         }
     }
 
+    // We want to merge own children like `I` in in `module A { interface I {} } module A { interface I {} }`
+    // We don't want to merge unrelated children like `m` in `const o = { a: { m() {} }, b: { m() {} } };`
+    function isOwnChild(n: Node, parent: NavigationBarNode): boolean {
+        const par = isModuleBlock(n.parent) ? n.parent.parent : n.parent;
+        return par === parent.node || contains(parent.additionalNodes, par);
+    }
+
     // We use 1 NavNode to represent 'A.B.C', but there are multiple source nodes.
     // Only merge module nodes that have the same chain. Don't merge 'A.B.C' with 'A'!
     function areSameModule(a: ModuleDeclaration, b: ModuleDeclaration): boolean {
@@ -383,7 +390,7 @@ namespace ts.NavigationBar {
 
         target.children = concatenate(target.children, source.children);
         if (target.children) {
-            mergeChildren(target.children);
+            mergeChildren(target.children, target);
             sortChildren(target.children);
         }
     }
diff --git a/tests/cases/fourslash/navigationBarMerging_grandchildren.ts b/tests/cases/fourslash/navigationBarMerging_grandchildren.ts
new file mode 100644
index 0000000000000..732b1794b6818
--- /dev/null
+++ b/tests/cases/fourslash/navigationBarMerging_grandchildren.ts
@@ -0,0 +1,44 @@
+/// <reference path="fourslash.ts"/>
+
+////const o = {
+////    a: {
+////        m() {},
+////    },
+////    b: {
+////        m() {},
+////    },
+////}
+
+verify.navigationTree({
+    text: "<global>",
+    kind: "script",
+    childItems: [
+        {
+            text: "o",
+            kind: "const",
+            childItems: [
+                { text: "m", kind: "method" },
+                { text: "m", kind: "method" },
+            ],
+        },
+    ]
+});
+
+verify.navigationBar([
+    {
+        text: "<global>",
+        kind: "script",
+        childItems: [
+            { text: "o", kind: "const" },
+        ],
+    },
+    {
+        text: "o",
+        kind: "const",
+        childItems: [
+            { text: "m", kind: "method" },
+            { text: "m", kind: "method" },
+        ],
+        indent: 1,
+    },
+]);