This study aimed to evaluate the Teachers' Registration Council of Nigeria (TRCN) Mandatory Continuing Professional Development Programme (MCPDP) for Primary School Teachers in Ekiti State, Nigeria, between 2011 and 2021. Seventy public primary schools were purposively selected with teachers who attended MCPDP in Ekiti State, while 166 teachers (attendees and non-attendees of the MCPDP) between 2011 and 2021 participated in the mixed methods study. Key informant interviews were conducted with eight school head teachers and two senior TRCN officials. Findings indicate that most teachers agreed that the MCPDP fostered their cross-fertilisation of ideas and experiences and professional competence. The MCPDP interview results also reported to have improved PSCTs' teaching competencies, commitment, and continuous relevance to the teaching profession. Thus, we recommend that the MCPD should be continued, and the TRCN should intensify the funding of the MCPD Programme and create more public awareness.