Online formative quizzes have been shown to be an effective tool for improving students' academic achievement. This quasi-experimental study investigated the effects of students' engagement in online formative quizzes on academic achievement in an undergraduate engineering course, employing a one-group post-test research design. Participants (n = 134) were assigned to a single group and voluntarily completed four online formative quizzes over an eight-week period. The dependent variable in this study was the participants' midterm exam grades in the course. Results showed that the average of the grades received from the online quizzes, the total number of quizzes completed, and the time spent on online formative quizzes were significant predictors of academic achievement. These findings suggest that engaging students in online formative quizzes can be an effective tool for supporting learning outcomes in engineering education. Limitations and suggestions for future research are also discussed.