The purpose of the current study was to examine the effect of divorce and parental death on mathematics self-efficacy and achievement in guidance school students. Using a causal comparison research design, we selected 45 divorce students and 45 students with parental death by available sampling. Also, 45 two-parent students randomly matched in age and grade with divorce and parental death groups. Mathematics Self-Efficacy Subscale was used for data collection. Students' math scores were used for assessing the mathematics achievement. Two-Way analysis of variance was used for analyzing the data. Results indicated that the mathematics self-efficacy and mathematics achievement were lower in students of divorce and students with parental death than two-parent students. Also Gender alone and interaction it with divorce and parental death is not affected the mathematics self-efficacy and achievement. Results have important implications in attending to negative consequences of divorce and parental death, especially low levels of mathematics self-efficacy and achievement in guidance school students.