In a larger study carried out by O'Sullivan "et al." to explore the perceptions and experiences of teachers in the Republic of Ireland and Northern Ireland who were engaged in continuing professional development (CPD), one of the significant findings to emerge was the key role of teacher motivation. The current study therefore focuses on the motivating and inhibiting factors involved and examines these against Herzberg "et al.'s" "two-factor theory" of motivation. The data collection methods involved two initial focus groups (n = 9) followed by questionnaires (n = 74). Motivation factors are considered at three levels: personal, school-related and system-wide. A Teacher CPD Motivation Model has been devised, which privileges the personal motivators of achievement, growth and advancement; promotes contingent factors such as interpersonal relations and school policy; and advocates a benevolent tangential factor of compulsory CPD. Implications are drawn out for initial teacher educators, school management teams and policy-makers in the field of teacher CPD in both Irish jurisdictions. These relate to the need for intentional and effective teacher CPD policies based on careful consideration of the factors that motivate teacher engagement, as expressed by the teachers themselves.