Corporate Social Responsibility (CSR) is key to achieving business success and serves as a strategic tool for survival in the competitive global business environment. There is a growing emphasis on sustainability, accountability, and ethical corporate governance and this has significantly increased global attention toward CSR. This study examined the effect of firm dynamics on CSR of listed Deposit Money Banks in Nigeria. Specifically, the study examines the effect of firm size, firm age, and firm profitability on CSR practices among banks quoted on the Nigerian Exchange Group. An ex-post facto research design was adopted using secondary data extracted from the annual reports and financial statements of sampled deposit money banks covering the period 2014–2024. Data were analyzed using descriptive statistics, correlation analysis, and panel regression techniques. The results show that firm size has a positive but insignificant effect on CSR, while firm age has a negative and insignificant relationship with CSR. The study further found that firm profitability has a significant negative effect on CSR among listed Deposit Money Banks in Nigeria. Overall, the study concluded that firm dynamics significantly influence the level and nature of CSR practices within the Nigerian banking sector. In view of the findings, the study recommended that banks should strengthen sustainability reporting frameworks, integrate CSR into strategic business policies, and improve stakeholder engagement to enhance sustainable development and corporate reputation.