The inability to handle financial risk as well as the possession of unhelpful financial risk attitudes by most bank customers poses considerable challenges to the banking sector. An individual customer who finds it difficult to handle significant decline in the value of their portfolio might resort to suicide or other negative life-threatening acts as means of ending their financial grief. Thus, it is important that customers are assisted to learn how to handle risks and/or losses related to their portfolio. This study investigated whether REBT-based business coaching can improve financial risk tolerance and financial risk attitudes among commercial bank customers in Nigeria. In this study which employed a two-group random assignment pretest–posttest design, 64 participants stayed in the REBT-based business coaching group whereas 63 participants stayed in the control group throughout the study period. The coaching program consisted of 8-weeks coaching activities. Quantitative data was collected before and immediately after the coaching program as well as 3-months later using measures of financial risk tolerance and financial risk attitudes. From the results, it was shown that REBT-based business coaching significantly improved the financial risk tolerance [F(1, 124) = 521.996, p < 0.05, η2p = 0.81] and financial risk attitudes [F(1, 124) = 582.613,p < 0.05, η2p = 0.83] of the commercial bank customers. Analysis of follow-up data revealed that these positive improvements were significantly sustained by study participants who received the REBT-based business coaching (financial risk tolerance [F(1, 126) = 339.492, p < 0.05, η2p = 0.73, \(\mathop {\Delta R}\nolimits^{2}\) = 0.767] and financial risk attitudes [F(1, 126) = 378.505, p < 0.05, η2p = 0.76, \(\mathop {\Delta R}\nolimits^{2}\) = 0.758]). Therefore, the REBT-based business coaching showed promising results by improving the financial risk tolerance and financial risk attitudes of bank customers. Large-scale coaching program based on REBT-based business coaching model can be deployed to reduce negative risk attitudes towards investment among other group of individuals in this and other study areas.