In Object-oriented programming languages like Java; it is the basic need to define a class within another class. These classes are known as nested classes or inner classes. The scope of a nested class is limited to its outer class. All the variables and methods of outer class are accessible inside inner class enhances encapsulation. Nested classes also help in packaging of the classes. In this paper, we propose a new metric, namely, Nested Class Complexity Metric (NCCM) to measure the complexity of nested classes and the results are compared with existing metrics, which are quite encouraging.