This study reports on the effectiveness and challenges of a formative assessment professional development program designed to address the challenges Kosovo teachers face in adequately using formative assessment in their classrooms. Selected teachers ("n" = 19) from Kosovo municipalities participated in the professional development training program. Data were collected from open-ended pre- and post-questionnaires, mentoring, and teacher portfolios. This mixed-methods approach utilized an inductive analysis approach. Positive results included teacher attitude changes toward and a better understanding of formative assessment and lesson planning. The study reveals the complexities of the cultural context in implementing peer and self assessment and the shifting of learning responsibility from teacher to student. Consequently, the study considers the impact of the cultural context on the many challenges teachers face in their practices. Thus, the study promotes further culturally contextual professional development to improve teacher practices, potentially impacting student outcomes and the educational system directly.