This study examined the effect of a self-monitoring strategy on EFL online learners' academic performance and motivational beliefs. A total of 90 college freshmen participated in the study, and instruments used in the study included two general English proficiency tests, a course-based reading comprehension test, and a modified version of the Motivated Strategies for Learning Questionnaire (MSLQ). Students were randomly assigned to a control group and an experimental group. Scores of the first general English proficiency test were used to verify students' starting points. The students in the experimental group employed a self-monitoring strategy during the semester. At the end of the semester, a course-based comprehension test and the second general English proficiency test were administered. During the semester, data from the modified MSLQ were collected at two points in time--the third week and the sixteenth week. Data analyses revealed that adopting a self-monitoring strategy resulted in better academic performance and a generally positive pattern of motivational beliefs, including adaptive levels of control of learning beliefs and perception of task value.