Background: Academic stress (AS) is recognized as a reproducible model of psychological stress that can affect immune system regulation. rare reports focus on the correlation between AS and oral microbial composition. Objective: This study aims to investigate the effect of academic examinations on immune function and oral microbial colonization among third-year medical students at the University of Sabratha. Methods: A descriptive cross-sectional study, questionnaires and saliva samples were collected from the students before, and after the end-term examination. A total of 84 students were initially registered, of whom 68 (61 females, 7 males aged 21–25 years) completed a questionnaire survey, and 69 oral samples were collected before examinations. Result: The finding demonstrated an increase in microbial colonization during the examination period compared to pre-examination samples. Elevated levels of psychological stress were also reflected in students' responses, indicating impaired immunity and a higher prevalence of stress-related symptoms. The association between elevated academic stress and reduced host defenses supports the hypothesis that stress-induced immune modulation can create favorable conditions for opportunistic microbial overgrowth. Moreover, during the examination, some genera of the oral-beneficial bacteria, markedly decreased in students with AS. On the other hand, the potential pathogenic genera, such as Streptococcus mutans Streptococcus pneumoniae, Candida sp significantly increased in the students with AS. And it effects on oral microbes displayed a gender difference among students. Conclusion: A high ratio of AS existed in the students during their examination period, and could significantly alter the oral microbial composition, decrease beneficial microbes, and promote potential pathogenic oral microbes............ Keyword.......... Psychological stress, Microbial colonization, cortisol, immunity, academic examinations, University of Sabratha.