This study is framed within Norton's notion of 'investment' to explore the factors influencing teachers' reasons and decisions to participate in continuing professional development (CPD) activities. Data were collected from 522 junior high school teachers in the Central region of Ghana using a survey and in-depth interviews. The findings reveal that teachers more frequently participated in informal CPD activities than in organised ones. Also, motivation to participate in CPD activities extended beyond intrinsic and extrinsic motivators to include sociocultural factors such as the nature of teachers' identity and agency, which were shaped by existing contextual conditions in teachers' professional practice. Such social conditions increased teachers' expectations of resources from CPD participation. Therefore, teachers invested in CPD activities where their expectations of resources from participation outweighed the cost to be expended on such involvement. The study opens up a debate for rethinking teacher motivation to include the notion of 'investment' to provide a much deeper understanding of the complexities involved in teachers' reasons for participating in CPD activities.