The study aimed to identify the relationship between each of the five big factors of personality, cognitive distortions, and achievement motivation. Also, to identify the level of each of the cognitive distortions and achievement motivation among the study sample. And, to examine the most common factor of the five big factors of personality. Also, to detect statistically significant differences in the level of cognitive distortions and the level of achievement motivation according to gender and academic major and examining the multiple liner regression between each of the five big factors of personality, achievement motivation and cognitive distortions. The sample of the study consisted of (404) eleventh grade students in North Al Sharqiyah schools in the Sultanate of Oman, who attended public schools during the academic year 2021/2022 AD. The researcher used three scales: the list of the five big factors of personality by Costa and McCrea (Costa & McCrea 1992), the cognitive distortion scale by Salah El-Din (2015), and the achievement motivation scale for children and adults by Harmans (1987). The results showed the following: The most common factor out of the five big factors is conscientiousness, and the least common factor is neuroticism. The level of cognitive distortions is generally low among the study sample, while the level of achievement motivation is generally high. The results also showed that there were no statistically significant differences in cognitive distortions and achievement motivation due to the variable of gender or academic major, and there was a statistically significant multiple liner regression between each of the five big factors, cognitive distortions, and achievement motivation. Keywords: The big five factors, Cognitive distortions, Achievement motivation.