Based on an integrated theory of formative assessment and self-regulated learning, this study investigated the relationship between students' perceived formative assessment practices of teachers and their motivational beliefs (self-efficacy and incremental beliefs of ability) and self-regulation strategies (metacognitive self-regulation and adaptive help seeking). Participants were 1,939 secondary school students (nested in 94 classes) from Singapore, who completed an online questionnaire. After controlling for gender, stream, and grade, we conducted a multilevel path analysis to examine the hypothesised relationships at both student and class levels. We found that at the student level, perceived formative assessment was associated positively with self-efficacy, incremental beliefs of ability, metacognitive self-regulation, and adaptive help seeking; at the class level, perceived formative assessment was associated positively with incremental beliefs of ability and adaptive help seeking. The findings highlight the importance of investigating formative assessment as a multilevel construct and its role in developing self-regulated learning of students.