Post-harvest losses of paddy in Sri Lanka are as high as 15 percent of total production. Of this, about 24 percent of losses occur during the threshing and cleaning stage with tractor treading being the most common paddy threshing method. In order to overcome these deficiencies, recently small and combined threshers have been introduced. This study attempted to determine the efficiency of different paddy threshing methods, and to estimate the profitability of small and combined thresher ownership. The level of adaptability of mechanical threshing methods (i.e., tractor treading, small and combined threshers) and the factors that influence the adoption of paddy threshers were also investigated. Multi-stage random sampling was adopted to collect primary data based on a structured questionnaire from Pollonnaruwa district, one of the major rice growing areas in the country. Financial analysis was employed to find the profitability of thresher ownership. An empirical model was estimated to evaluate the efficiency of mechanical threshing methods based on the savings of labour and material. Logit model was fitted to identify the factors affecting thresher adoption. The study revealed that on average, small and combined threshers increase the net income per ha by Rs.6, 345 and Rs.9, 071 respectively, compared to tractor treading. Combined thresher ownership was found to be more profitable than small thresher ownership. The minimum economic operational area for tractor treading, small thresher and combined thresher were 41.78 ha/yr, 3.47 ha/yr and 20.97 ha/yr, respectively. Monthly income, wealth, cultivated extent and farming experiences were significantly related to the adoption of both small and combined threshers. Since replacing tractor treading by threshing machines reduces the post-harvest losses and increases the net income it is recommended that the availability of both types of threshers to be increased depending on farmer resource endowment.