Software cost estimation is an essential aspect of software project management and therefore the success or failure of a software project depends on accuracyin estimating effort, time and cost. Software cost estimation is a scientific activity that requires knowledge of a number of relevant attributes that will determine which estimation method to use in a given situation. Over theyears various studies were done to evaluatesoftware effort estimation methods however due to introduction of new software development methods, the reviews havenot capturednew software development methods.Agile software development method is one of the recent popular methodsthat werenot taken into account inprevious cost estimation reviews.The main aim of this paper is to review existing software effort estimationmethodsexhaustivelyby exploring estimation methods suitable for new software development methods