Microcredentials are a promising means for expanding teacher access to high quality professional development. This study examined the effectiveness of online, self-paced microcredential courses designed for teachers working in underserved rural communities. The content of these competency-based microcredentials centered on recommended instructional strategies from the What Works Clearinghouse practice guides of the Institute of Education Sciences. To examine the effectiveness of the microcredentials, teacher participants were randomly assigned to one of two microcredentials on elementary mathematics, one on teaching word problems and the other on teaching fractions. Participants (n = 573) completed the pre-post assessments for each course, and follow-up interviews were conducted with a subset of participants (n = 65). Results revealed both microcredential courses were effective in increasing participants' knowledge of evidence-based instructional practices targeted in their respective microcredential. The authors suggest that online microcredentials present an accessible and affordable means for teacher professional development, especially in locations or situations where face-to-face professional development is challenging.