Background: Primary Health Care (PHC) was introduced as the first level of health services delivery after Alma-Ata declaration. However, after forty years, it needs to be more trustful to achieve its predefined objectives. Public trust in PHC is one of the neglected issues in the context. The aim of this study is to evaluate public trust in PHC in Iran. Methods: The present investigation is a household survey conducted in East Azerbaijan Province, Iran. Two-stage cluster sampling method with Probability Proportional to Size (PPS) approach was used. Totally, 1178 households were enrolled in the study. PHC trust questionnaire and Ultra-short version of SocioEconomic Status assessment questionnaire (SES-Iran) was used for data collection. Data were analyzed using STATA software (version 15) through descriptive statistics and linear regression. Results: The mean ± SD age of the participants was 41.2 ± 15.1 and most (53.7%) were female. Mean score of PHC trust was 56.9 ± 24.7 (out of 100). It was significantly different between residents of Tabriz (the capital of province) and other cities in the province (p < 0.001). Linear regression showed that younger age, gender, insurance type, being married, and households higher socioeconomic status had a significant positive effect on PHC trust level with R 2 = 0.14383. Conclusions: Public trust in PHC system in Iran needs to be improved. Individual variables had a small but key role in trust level. PHC trust cannot be only affected by individual's variables and experiences but also by health system and health providers' characteristics and public context in which PHC system exists. PHC trust level could be used as a public indicator in health systems especially in Low and Middle Income Countries (LMIC) to contribute in system strengthening policies at the national and international levels.