Today, all the sectors of world economy are facing huge challenges to deal with the environmental problems and their related impacts in their day to day businesses. In Sri Lanka, banks are launching green banking initiatives in recent years. Apparently, there are lacunas in empirical studies undertaken in Sri Lankan context regarding green banking and bank's environmental performance. Hence, the objective of this paper is to measure the impact of green banking practices on bank's environmental performance. In order to achieve the objective, primary data were collected from 155 employees of selected bank branches and the structured questionnaire was administered to collect the data. The data were analyzed by using univariate, bivariate and multivariate analyses. The finding of the study revealed that green banking practices have positive and significant impact on bank's environmental performance in overall. And it also found that employee related practice, daily operation related practice and bank's policy related practice were found to have positive and significant impact on bank's environmental performance however, customer related practice has no significant impact on bank's environmental performance. The current study will be vital in understanding the empirical knowledge regarding the impact of green banking practices on bank's environmental performance.