Mental morbidities have been widely investigated at Primary Health Care (PHC) worldwide, but no data available in Palestine have discussed these diseases' burden. This study aimed to assess the prevalence of psychological morbidity among primary health care attendees and related factors. A cross-sectional design was adopted in this research. We collected data from primary healthcare center attendees from Sept 2019 to Jan 2020, using an interviewer-administered questionnaire called the Four-Dimensional Symptom Questionnaire. It is a valid tool that can be used in a primary healthcare setting. The Chi-square test explored psychological morbidity risk factors, and the multivariable logistic regression model was used to adjust for confounders. The study included four hundred clients >18 years of age; 287 (71.8%) were females, and 209 (52.3%) were >50 years of age. The prevalence for high psychological morbidity of any type was 63.9% (95% CI: 58.8%-68.7%), while 24.9% (99 clients) reported very high psychological morbidity. Very high psychological morbidity was significantly higher among unmarried [adjusted OR = 2.7 (95%CI= 1.4-5.4)], lower educational level (less than 12 years schooling) [adjusted OR=4.0, 95%CI (1.8-4.8)], and clients with high distress [adjusted OR=15.6, 95%CI (7.9-30.9)]. In conclusion, the high prevalence of psychological morbidity identified in this study highlights the importance of early detection and management, especially among unmarried, less educated, and distressed primary health care attendants. Early interventions are of high value to reduce patient suffering, decrease the financial strain on the health system, and improve the quality of care.