Deposit mobilization is one of the key activities that contribute to the efficiency of banks (Yakubu, 2020) Being in the sixty-first place in the emerging economics market list out of sixty-six countries, deposits are important for Sri Lankan bank operations. Many businesses rely seriously on bank loans as a source of financing. From the bank's perspective deposits is the major indicator of how much funds are available for lending-ABSTRACT Purpose: The purpose of this research is to examine the main factors determining the growth of commercial bank deposits in Sri Lanka for the period 1999 -2017.Design/Methodology/Approach: The research uses micro and macro level data collected from purposive random basis. The autoregressive distributed lag approach used to determine the significant micro and macro factors of banks deposit growth.Findings: The results show that bank steadiness, the productivity of the banking sector, the large supply of capital, economic growth and inflation are important long-term determinants of deposit growth. The findings additionally show that for bank deposit mobilization, only branch expansion and large money supply are important in the short term.Originality / Value: This study divergent from the extant from the scope empirical studies that focus on the determinants of individual savings behavior in Sri Lanka. The research investigates distinctly how bank characteristics affect deposit growth in view of the short-and long-run time dimensions, thus offering a relatively groundbreaking effort arena.Research Limitations/Future Research Directions -This is based on only for a period of eighteen years and only few determinants have been used for the study due to data availability. However, this study can be extended by using other determents of bank deposits and considering a longer time horizon.