This study aimed to examine the correlation between optimism-pessimism and personality traits (extraversion, introversion, emotional stability and neuroticism), also aimed to identify the prevalence of optimism and pessimism in the study sample according to the variable sex, academic specialization, level of study, and grade point average. The study sample consisted of (534) students among undergraduate students enrolled in the Hashemite University during the summer semester 2010/2011. Results of study revealed that: A positive correlation relationship and statistically significant between optimism and introversion. Statistically significant positive correlation relationship between pessimism emotional equilibrium, and the pessimism emotion. Statistically significant negative correlation relationship between pessimism and extraversion, and between pessimism and introversion. Differ in the prevalence of optimism in three levels (high, moderate, and low) according to the variables sex, area of study, level of study, and grade point average. Different ratios of the three levels is widespread pessimism (high, moderate, and low) according to the variables sex, area of study, level of study, and grade point average. Statistically significant differences between males and females in the prevalence of trait optimism in favor of male students. The differences are statistically significant at the level of significance (0.05) between the academic level (first, second, third, and fourth) in the trait of optimism for the benefit of students who are in the level of the first, second, and third year. The presence of significance interaction between sex and grade point average on a feature of pessimism. The presence of significance interaction between specialization and grade point average on a feature of pessimism.