The main purpose of this study was to explore how irrational beliefs, self-efficacy belief, self-perception and the fear of negative evaluation account for university students' academic procrastination behaviors. It was also intended to determine whether academic procrastination behavior differs depending on gender, school attended, class level and academic success. The study group consisted of 1011 university students (582 females, 429 males) studying atvarious schools of the Karadeniz Technical University, Turkey. The academic procrastination scale, irrational belief scale, general self-efficacy scale, social comparison scale, fear of negative evaluation scale and a personal information form were used for data collection. Data analysis was performed on SPSS 15.00 software. The study findings show that academic procrastination behavior differs depending on gender, class level and academic success, but not on the faculty attended. In addition, a positive relation was determined between academic procrastination and irrational beliefs and the fear of negative evaluation, and a negative relation between self-efficacy belief and self-perception. Irrational beliefs, self-efficacy belief, self-perception and fear of negative evaluation were identified as predictors of academic procrastination. The results are discussed in the light of the literature and suggestions are proposed based on the findings.