Background: Avoidable hospitalizations (AHs) are defined as hospitalizations that could have been prevented through timely and effective services. AHs are, therefore, an indicator used to evaluate the access and effectiveness of primary health care services. Methods: A retrospective time-series study spanning 8 years (2006–2013) was conducted to determine the relationship between AHs and gender, age, and access to primary health care physicians in rural areas in Tehran province, the capital of Iran. The total number of avoidable hospitalizations was 22,570; logistic regression was estimated for each year separately. Results: Total hospitalizations and AHs increased during the study period, especially during the first 3 years of the study. AHs, as a percentage of total hospitalizations, did not change significantly throughout the study years. This value was 22.3% during the first year of study and varied between 17% and 19.6% from 2007 to 2013. No statistically significant relationship was seen between AH occurrence and access to a physician during the study years. Conclusion Increasing access to primary health care physicians cannot necessarily result in decreased AHs. Considering the factors influencing AHs while designing and implementing the family physicians program is important to achieve the expected results regarding the effectiveness of primary health care services.