The Current study investigated the effect of the 5E learning cycle in which the simulations were integrated on pre-service science teachers' achievement in photoelectric subject. Four sophomore level classes with their 140 students participated in the research and a quasi-experimental design was used. The classes were randomly assigned into one of the two treatment groups. The experimental group (n1 = 69, male = 16, female = 53) studied photoelectric effect with the developed instruction and the control group (n2 = 71, male = 19, female = 52) studied the same subject with traditional instruction. Achievement test and open-ended exam were administered to measure students' pre-and-post achievements. The main effect of treatment on post-tests scores was examined via MANCOVA with pre-achievement scores used as covariate. The analyses yielded significant treatment effect on the collective dependent variables. Follow up ANCOVA results indicated that the instruction developed for the experimental group affected participants' post-achievement and post-open-ended exam scores significantly. Extensive analyses of the open-ended exam items showed that some of the participants were considering the supplied potential as the preliminary condition for the current flow in photocell circuit. The instructors or researchers would develop their treatments by integrating scientifically well-developed simulations into 5E learning cycle and use them in their lessons to promote learners' achievements.