Photoelectric effect is regarded as one difficult topic in physics for science students because it is the abstract and multidimensional phenomenon. This study aims to develop the learning unit incorporated simulation and game with the 5E learning cycle for promoting the grade 12 science students' understanding of photoelectric effect and learning attitudes. The created learning unit was implemented with 31 grade 12 students in Bhutan. The students' pre- and post-understanding of photoelectric effect were measured by the Photoelectric Evaluation Conceptual Evaluation Test (PECE). In addition, the students' attitudes to the unit were explored by using the Multimedia Attitude Survey (MAS), individual interviews, and reflective journals. The quantitative data were analyzed by calculating for mean, standard deviation, and t-test. The qualitative data were analyzed by inductive analysis. The results from PECE revealed that the mean scores of students' pre- and post-tests were 12.94 (S.D. = 3.81) and 16.94 (S.D. = 3.12), respectively. The simulation and game based learning unit significantly helped the participating students improve their understanding of photoelectric effect (t = 7.79, p < 0.05). In addition, the students expressed their positive attitudes to the learning unit. The implications in teaching physics by game and simulation embedded in the 5E learning cycle are also discussed.