In this longitudinal study, the authors investigate changes in teachers’ mathematics knowledge during a mathematics content course focused on real-world applications and during a content/pedagogy hybrid course designed specifically for elementary teachers. The authors used two popular assessments in the United States: (1) Learning Mathematics for Teaching (LMT) and (2) Diagnostic Teacher Assessments in Mathematics and Science (DTAMS). The findings reveal that teachers made large gains on both measures. However, the LMT better captured gains made during the hybrid course, whereas DTAMS better detected gains during the mathematics course. Furthermore, the patterns of change differed during the two courses, with the LMT scores increasing during the hybrid course only and the DTAMS scores increasing over the two courses.