Professional development for teachers propels schools to excellence and contributes to school growth. Therefore, the purpose of this study was to examine the role of teachers' personal characteristics, perception towards Continuous Professional Development (CPD) and support of school leaders in the implementation of teachers' CPD at Finote Selam town secondary school in Ethiopia. To accomplish this, Ecological Theory served as a theoretical lens, and a convergent parallel mixed design was used. A questionnaire was used to collect data from 304 teachers selected using a comprehensive sampling strategy, as well as 11 interviewers. As findings, teachers' implementation of CPD has no correlation with age, length of service, and perception of teachers towards CPD. However, there is a significant, strong, and positive relationship between teachers' implementation of CPD and school leaders' contribution to CPD. The support of school leaders explains 39.6 % of the total variance of teachers' CPD implementation. Finally, lack of good school culture among use in professional development activities, lack of commitment, lack of funding, and lack of common understanding related to CPD were the most prominent challenges affecting teachers' implementation of CPD. The findings provide theoretical implications to the literature and practical implication to educational institution leaders by identifying the main challenges of teachers in the implementation of CPD.