Introduction: The widespread use of smart phones has given rise to concerns about addictive behaviors leading to the emergence of smart phone addiction and nomophobia, and their potential impact on work performance. Aim of Work: This study aims at exploring smartphone addiction predictors and smartphone addiction association with nomophobia and job performance among office workers at faculty of Medicine, Suez Canal University. Materials and Methods: A cross-sectional study was conducted on 130 office workers employed in faculty of Medicine, Suez Canal University, Egypt. The participants were chosen using convenient sampling. The data was collected through a self-administered questionnaire that included personal data, smartphone usage data, an assessment of smartphone addiction using the short version of the Smart Phone Addictions Scale, an assessment of nomophobia using the Nomophobia Questionnaire, and an assessment of job performance using the Health and Work Performance Questionnaire. Results: The current study found a high prevalence of smartphone addiction, as 58.5% of office workers classified as addicted. All study participants displayed nomophobic behaviors, with a mild level prevailing (54.6%). Furthermore, a moderate positive correlation was observed between smartphone addiction and nomophobia (r = 0.531, p < 0.001). Additionally, a moderate negative correlation was found between job performance and smartphone addiction (r=-0.452, p < 0.001), as well as between job performance and nomophobia (r=-0.478, p < 0.001). Regression analysis revealed that duration of daily smartphone use, playing games, use of smartphone for entertainment purposes, and nomophobia were significant predictors of smartphone addiction. Conclusion and Recommendation: The present study highlights the high prevalence of smartphone addiction and nomophobia among office workers. They both affect job performance negatively. Addressing these issues is important for well-being and productivity in the workplace.