Three mathematics teacher educators who were assigned to teach fundamental concepts of algebra course in a teacher education college, as well as their prospective elementary mathematics teachers who took the course, took part in a job embedded, context-specific, and content-based comprehensive professional development (PD) program on assessment for learning (AfL). Three teacher educators and 129 prospective elementary mathematics teachers from three teacher education colleges took part in the study. The findings demonstrated that prospective elementary mathematics teachers in the intervention group significantly outperformed prospective teachers in both of the comparative groups in their post-test scores in algebra. Furthermore, it was found out that after the intervention, there was no statistically significant mean difference among achiever levels in the treatment group on post-test scores, despite a statistically significant mean difference among achiever levels in their pre-test scores. This research adds to our knowledge of the impact of comprehensive, job-embedded, context-specific, and content-based PD on prospective teachers' achievements in algebra in elementary school mathematics teacher education. Implications of implementing AfL as well as recommendations for further research are highlighted.