In this study, the effect of algorithm education on pre-service teachers' computational thinking skills and computer programming self-efficacy perceptions were examined. In the study, one group pretest posttest experimental design was employed. The participants consisted of 24 (14 males and 10 females) pre-service teachers, majoring in Computer Education and Instructional Technology (CEIT). In order to determine the pre-service teachers' computer programming self-efficacy perceptions, the Computer Programming Self-Efficacy Scale was used, whereas Computational Thinking Skills Scale was used to determine their computational thinking skills. The Wilcoxon Signed-Rank Test was used to analyze the differences between pretest and posttest scores of students' computer programming self-efficacy perceptions and computational thinking skills. Throughout the practices, 10 different algorithmic problems were presented to the students each week, and they were asked to solve these problems using flow chart. For 13 weeks, 130 different algorithmic problems were solved. Algorithm education positively and significantly increased students' simple programming tasks, complex programming tasks and programming self-efficacy perceptions. On the other hand, algorithm education had a positive and significant effect only on students' algorithmic thinking sub-dimension but did not have any effect on other sub-dimensions and computational thinking skills in general.