Student self-regulation is associated with mathematics achievement in Nigerian primary schools, and formative assessment holds promise for increasing self-regulation. However, to date no research has explored teacher professional development (PD) for formative assessment and its effects on students' self-regulation in Nigerian primary schools. This quasi-experimental nonequivalent control group design used Desimone's teacher professional development conceptual framework, Popham's model for practicing formative assessment, and Zimmerman's concept of self-regulated learning. Research questions concerned whether differences existed in teachers' practice and students' self-regulation between two groups of Nigerian primary school mathematics teachers who received variations of professional development. The sample was 13 volunteer mathematics teachers (7 in a workshop plus follow-up group and 6 in a workshop-only group) and 183 students from 7 primary schools. Teacher formative assessment quality (FAQ) data was collected from 3 classroom observations and student end-of-project self-regulation was measured via a questionnaire. Descriptive analysis at the teacher level showed that teachers in the workshop-plus group had a higher level of FAQ than workshop-only teachers. A t test showed students with workshop-plus teachers had significantly higher self-regulation scores on average than students with workshop-only teachers, although FAQ did not correlate with students' self-regulation scores, possibly due to a small sample size. This study contributes to social change by providing supporting evidence for school administrators to provide workshop plus follow-up coaching PD to teachers to increase the quality of formative assessment, which may have implications for improving mathematics achievement among primary students in Nigeria. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]