Abstract: Dengue is a mosquito-borne viral disease and it spreads rapidly in many parts of the world including Sri Lanka. The commercial capital of Sri Lanka is Colombo and Colombo Municipal Council (CMC) is the largest and financial centre in Sri Lanka. Reports in health ministry of Sri Lanka say that, more dengue cases are reported in western part of the country, particularly, from areas of CMC. The study mainly focused on the dengue cased reported in the areas of CMC in Sri Lanka. The purpose of forecast is to the plan the future activities. Thus in this study, a statistical model is fitted to predict the future dengue cases in the area of CMC. Then relevant official can take necessary action to control the future dengue cases in CMC. All necessary tests are employed to build the model. Hence the predicted values are obtained. Accordingly, more than 1500 dengue cases are expected in last six months in the year 2016.