diff --git a/SwiftyAttributes/Sources/common/Operators.swift b/SwiftyAttributes/Sources/common/Operators.swift
index 50a00e1..17efba0 100644
--- a/SwiftyAttributes/Sources/common/Operators.swift
+++ b/SwiftyAttributes/Sources/common/Operators.swift
@@ -16,3 +16,22 @@ public func + (lhs: NSAttributedString, rhs: NSAttributedString) -> NSMutableAtt
     combinedString.append(rhs)
     return combinedString
 }
+
+/**
+ Addition and assign operator. Creates a concatenated string and assigns it to the left value.
+ */
+public func += (lhs: inout NSAttributedString, rhs: NSAttributedString) {
+    lhs = lhs + rhs
+}
+
+public func += (lhs: inout NSMutableAttributedString, rhs: NSAttributedString) {
+    lhs = lhs + rhs
+}
+
+public func += (lhs: inout NSAttributedString, rhs: NSMutableAttributedString) {
+    lhs = lhs + rhs
+}
+
+public func += (lhs: inout NSMutableAttributedString, rhs: NSMutableAttributedString) {
+    lhs = lhs + rhs
+}
diff --git a/SwiftyAttributesTests/Operators_Tests.swift b/SwiftyAttributesTests/Operators_Tests.swift
index ce2e772..131b481 100644
--- a/SwiftyAttributesTests/Operators_Tests.swift
+++ b/SwiftyAttributesTests/Operators_Tests.swift
@@ -24,5 +24,69 @@ class Operators_Tests: XCTestCase {
         ]
         XCTAssertEqual(newString.attributes(at: lhs.length + 1, effectiveRange: nil) as NSDictionary, rightAttributes as NSDictionary)
     }
+    
+    //  NSAttributedString + NSAttributedString
+    func testOverloadedAssignedAdditionOperator1() {
+        let lhs = "Hello".withFont(.systemFont(ofSize: 19)) as NSAttributedString
+        let rhs = "World".withTextColor(.magenta).withBackgroundColor(.orange).withFont(.boldSystemFont(ofSize: 24)) as NSAttributedString
+        var newString = lhs
+        newString += rhs
+        let leftAttributes: [NSAttributedString.Key: NSObject] = [.font: Font.systemFont(ofSize: 19)]
+        XCTAssertEqual(newString.attributes(at: 0, effectiveRange: nil) as NSDictionary, leftAttributes as NSDictionary)
+        let rightAttributes: [NSAttributedString.Key: NSObject] = [
+            .foregroundColor: Color.magenta,
+            .backgroundColor: Color.orange,
+            .font: Font.boldSystemFont(ofSize: 24)
+        ]
+        XCTAssertEqual(newString.attributes(at: lhs.length + 1, effectiveRange: nil) as NSDictionary, rightAttributes as NSDictionary)
+    }
+    
+    //  NSMutableAttributedString + NSAttributedString
+    func testOverloadedAssignedAdditionOperator2() {
+        let lhs = "Hello".withFont(.systemFont(ofSize: 19))
+        let rhs = "World".withTextColor(.magenta).withBackgroundColor(.orange).withFont(.boldSystemFont(ofSize: 24)) as NSAttributedString
+        var newString = lhs
+        newString += rhs
+        let leftAttributes: [NSAttributedString.Key: NSObject] = [.font: Font.systemFont(ofSize: 19)]
+        XCTAssertEqual(newString.attributes(at: 0, effectiveRange: nil) as NSDictionary, leftAttributes as NSDictionary)
+        let rightAttributes: [NSAttributedString.Key: NSObject] = [
+            .foregroundColor: Color.magenta,
+            .backgroundColor: Color.orange,
+            .font: Font.boldSystemFont(ofSize: 24)
+        ]
+        XCTAssertEqual(newString.attributes(at: lhs.length + 1, effectiveRange: nil) as NSDictionary, rightAttributes as NSDictionary)
+    }
+    
+    //  NSAttributedString + NSMutableAttributedString
+    func testOverloadedAssignedAdditionOperator3() {
+        let lhs = "Hello".withFont(.systemFont(ofSize: 19)) as NSAttributedString
+        let rhs = "World".withTextColor(.magenta).withBackgroundColor(.orange).withFont(.boldSystemFont(ofSize: 24))
+        var newString = lhs
+        newString += rhs
+        let leftAttributes: [NSAttributedString.Key: NSObject] = [.font: Font.systemFont(ofSize: 19)]
+        XCTAssertEqual(newString.attributes(at: 0, effectiveRange: nil) as NSDictionary, leftAttributes as NSDictionary)
+        let rightAttributes: [NSAttributedString.Key: NSObject] = [
+            .foregroundColor: Color.magenta,
+            .backgroundColor: Color.orange,
+            .font: Font.boldSystemFont(ofSize: 24)
+        ]
+        XCTAssertEqual(newString.attributes(at: lhs.length + 1, effectiveRange: nil) as NSDictionary, rightAttributes as NSDictionary)
+    }
+    
+    //  NSMutableAttributedString + NSMutableAttributedString
+    func testOverloadedAssignedAdditionOperator4() {
+        let lhs = "Hello".withFont(.systemFont(ofSize: 19))
+        let rhs = "World".withTextColor(.magenta).withBackgroundColor(.orange).withFont(.boldSystemFont(ofSize: 24))
+        var newString = lhs
+        newString += rhs
+        let leftAttributes: [NSAttributedString.Key: NSObject] = [.font: Font.systemFont(ofSize: 19)]
+        XCTAssertEqual(newString.attributes(at: 0, effectiveRange: nil) as NSDictionary, leftAttributes as NSDictionary)
+        let rightAttributes: [NSAttributedString.Key: NSObject] = [
+            .foregroundColor: Color.magenta,
+            .backgroundColor: Color.orange,
+            .font: Font.boldSystemFont(ofSize: 24)
+        ]
+        XCTAssertEqual(newString.attributes(at: lhs.length + 1, effectiveRange: nil) as NSDictionary, rightAttributes as NSDictionary)
+    }
 
 }