Reversing the traditional classroom activities, in the flipped classroom model students view lectures at home and perform activities during class period inside the classroom. This study investigated the effect of a flipped classroom implementation on college physics students' motivation and understanding of kinematics graphs. A Solomon four-group design employing quantitative and qualitative methods was used to gather data. Four college physics sections participated in this study. Two groups received a researcher-developed, flipped classroom, instructional material over the course of 8 sessions. Test for Understanding Graphs in Kinematics (TUG-K) gain scores (post-test - pretest) were significantly higher for the experimental groups (M = 1.87, SD = 2.909) compared with the control groups (M = 0.54, SD = 1.853). However, Physics Motivation Questionnaire II (PMQII) did not show a significant difference. The flipped classroom may enhance students' learning of kinematics graphs by improving their level of understanding, but was shown to have no effect on their motivation.