This study examines the effects of math readiness and student course behavior (e.g., attendance, participation, homework completion) on knowledge gain and course success using two samples of students enrolled in foundational skills (noncredit-bearing) mathematics courses. As hypothesized, entering student mathematics readiness and course behavior predicted posttest mathematics knowledge. Posttest knowledge and course behavior predicted course success (i.e., passing the course). Results highlight the importance of mathematics readiness and student behavior for understanding mathematics knowledge gains and course success. Implications for institutional policy and practice using effective diagnostic testing and behavioral monitoring are discussed.