diff --git a/lib/rules/operator-assignment.js b/lib/rules/operator-assignment.js
index 63982cf3920..ea6d2905c46 100644
--- a/lib/rules/operator-assignment.js
+++ b/lib/rules/operator-assignment.js
@@ -194,7 +194,17 @@ module.exports = {
                             ) {
                                 rightText = `${sourceCode.text.slice(operatorToken.range[1], node.right.range[0])}(${sourceCode.getText(node.right)})`;
                             } else {
-                                rightText = sourceCode.text.slice(operatorToken.range[1], node.range[1]);
+                                const firstRightToken = sourceCode.getFirstToken(node.right);
+                                let rightTextPrefix = "";
+
+                                if (
+                                    operatorToken.range[1] === firstRightToken.range[0] &&
+                                    !astUtils.canTokensBeAdjacent(newOperator, firstRightToken)
+                                ) {
+                                    rightTextPrefix = " "; // foo+=+bar -> foo= foo+ +bar
+                                }
+
+                                rightText = `${rightTextPrefix}${sourceCode.text.slice(operatorToken.range[1], node.range[1])}`;
                             }
 
                             return fixer.replaceText(node, `${leftText}= ${leftText}${newOperator}${rightText}`);
diff --git a/tests/lib/rules/operator-assignment.js b/tests/lib/rules/operator-assignment.js
index fe7b326a10a..06a0e40e707 100644
--- a/tests/lib/rules/operator-assignment.js
+++ b/tests/lib/rules/operator-assignment.js
@@ -230,6 +230,31 @@ ruleTester.run("operator-assignment", rule, {
         output: "foo = foo * (bar + 1)",
         options: ["never"],
         errors: UNEXPECTED_OPERATOR_ASSIGNMENT
+    }, {
+        code: "foo+=-bar",
+        output: "foo= foo+-bar", // tokens can be adjacent
+        options: ["never"],
+        errors: UNEXPECTED_OPERATOR_ASSIGNMENT
+    }, {
+        code: "foo+=+bar",
+        output: "foo= foo+ +bar", // tokens cannot be adjacent, insert a space between
+        options: ["never"],
+        errors: UNEXPECTED_OPERATOR_ASSIGNMENT
+    }, {
+        code: "foo+= +bar",
+        output: "foo= foo+ +bar", // tokens cannot be adjacent, but there is already a space between
+        options: ["never"],
+        errors: UNEXPECTED_OPERATOR_ASSIGNMENT
+    }, {
+        code: "foo+=/**/+bar",
+        output: "foo= foo+/**/+bar", // tokens cannot be adjacent, but there is a comment between
+        options: ["never"],
+        errors: UNEXPECTED_OPERATOR_ASSIGNMENT
+    }, {
+        code: "foo+=+bar===baz",
+        output: "foo= foo+(+bar===baz)", // tokens cannot be adjacent, but the right side will be parenthesised
+        options: ["never"],
+        errors: UNEXPECTED_OPERATOR_ASSIGNMENT
     }]
 
 });