Procrastination is an undesirable and maladaptive behavior common especially in academic domain. Research studies have shown that it is one of the common barriers to academic success since it decreases the quality and quantity of work. There has been intense body of literature on procrastination and its reasons in different age groups. However, direct comparison of different academic grade levels on procrastination prevalence and its reasons has drawn less attention in the literature. Hence, the purpose of the present research was to investigate the levels, prevalence and the reasons of academic procrastination on high school, undergraduate and graduate students. In this respect, Procrastination Assessment Scale-Student (PASS) was administered to a total of 448 students: 149 (83 female; 66 male) were high-school, 150 (80 female; 70 male) undergraduate and 148 (84 female; 64 male) graduate students. The average age was 15.5 years old for high-school, 20.4 years old for undergraduate, and 25.5 years old for graduate students. Results showed a significant difference in procrastination among these three groups. Specifically, undergraduate students (M = 20.1; SD = 3.8) claimed to procrastinate more than graduate (M = 18.5; SD = 4.1) and high school students (M = 17.2; SD = 4.5). 37% of high school students and 56% of undergraduate students claimed to be nearly always or always procrastinator on studying for exams, while graduate students (39%) procrastinate more on writing term papers. High school students engage in procrastination due to the reason of perfectionism, difficulty in making decision, laziness and risk taking; while undergraduates procrastinate due to lack of assertion and aversiveness of tasks. Graduate students procrastinate due to fear of failure, rebellion against control and laziness.