Introduction: Depression is a common medical illness with a multifactorial predisposition. The prevalence of depression in Saudi Arabia has been estimated in elderly at 1999 to be around 39 percentage of patient that have been seen in primary health care center. There is no study conducted in AlAhsa, Therefore, this study aims to assess the prevalence of depression among patients attending Primary Health Care Centers (PHCC) in AlAhsa, Saudi Arabia, to identify the risk factors as well as the severity of depression based on PHQ 9, and to test the sensitivity and specificity of PHQ 2 and PHQ 9. Methods: This is a cross sectional study conducted in AlAhsa, Saudi Arabia. Participants were all patients attending primary health care centers of three different sectors in the region. Data was collected using PHQ 2 and PHQ 9 questionnaires through an individual interview carried out by trained medical students. Results: A total of 314 (79.6 percentage females, 20.4 percentage males) were screened with PHQ-9. Totally, depression was detected among 97 (30.9 percentage) of participants. 22 percentage had mild depression, 6.1 percentage had moderate depression, and 2.8 percentage had moderately severe to severe depression. Regarding determinants of depression among PHCCs attendants, it was clear that depression was detected among 75 percentage of participants due to medications side effect, 45.7 percentage with a positive family history, and 36.5 percentage was due to stressful events, Other factors including age, gender, job nature, and having chronic health problems were insignificantly associated with developing depression. In the current study we found the sensitivity for PHQ 2 of 93.8 percentage, specificity of 72.4 percentage. Which means that PHQ 2 is excellent tool for excluding depressive status and dependable in identifying cases. Conclusion: In this study, we found that depression tends to be prevalent among patients attending PHCCs in AlAhsa population. Certain factors were associated with higher chances of having depression. Furthermore, this study emphasizes on the use of PHQ 2 as a screening tool for depression, which was found to be excellent tool for ruling out and ruling in depressive cases.