This study compared the effects of using physical robots (LEGO Mindstorms) and robot simulators (LEGO Mindstorms Simulator, LMS) in teaching novice programming concepts. A quasi-experiment design was implemented in this study. Four classes of high school students, totaling 151 students, participated in the study. Two classes of 76 students used the physical robots to learn programming, whereas the other two classes of 75 students used LMS. The students' post-experiment achievement tests, replies on questionnaires, and focus group interview data were collected and analyzed. The findings of the study were: (1) no significant difference was found on students' performance between the physical robot group and the simulator group, (2) the physical robot group demonstrated more positive attitudes toward the learning activities, and (3) the physical robot group indicated that they could better imagine the program behaviors.