Leptospirosis is a severe infectious disease caused by bacteria. In Sri Lanka, it is one of the main communicable diseases. From 2010 to 2017, more than 4000 outbreaks of leptospirosis per year were reported to the epidemiology unit. Although outbreaks were reported in all the districts throughout the year, Colombo, Kalutara, Gampaha, Ratnapura, Galle, Matara, Kegalle, Matale and Kurunegala were named as leptospirosis endemic districts in Sri Lanka. In the first half of the year 2018, more than 2000 outbreaks had been reported island wide. Nearly half of the total outbreaks in the island were from five districts namely, Colombo, Gampaha, Kalutara, Ratnapura, Kurunegala and considered them, in this study, as the “selected five districts”. Therefore, the objective of this study is to model the outbreaks reported in these five districts of Sri Lanka. The relevant techniques and the appropriate tests were employed to develop model to forecast the outbreaks of leptospirosis in those districts. This study concludes that, leptospirosis outbreaks in Colombo, Gampaha, Kurunegala districts are decreasing while in Kalutara and Ratnapura districts the outbreaks are in increasing trend among the selected five districts of Sri Lanka in the study period. Over 92% accuracy of the best fitted model was developed. Hence the estimated outbreaks only in the last nine months from the selected five districts of Sri Lanka in the year 2018 will be 1200.