BACKGROUND: Identifying breast cancer risk factors is a critical component of preventative strategies for this disease. This study aims to identify modifiable and non-modifiable risk factors of breast cancer in Iranian women. METHODS: We used international databases (PubMed/Medline, Scopus, Web of Knowledge, and Embase) and national databases (SID, Magiran, and ISC) to retrieve relevant studies until November 13, 2022. The odds ratio (OR) with a 95% confidence interval using the random-effect model was used to estimate the pooled effect. The publication bias was assessed by the Egger and Begg test. A sensitivity analysis was conducted to evaluate the effect of each included study on the final measurement. RESULTS: Of the 30,351 retrieved articles, 24 matched case-control records were included with 12,460 participants (5675 newly diagnosed cases of breast cancer and 6785 control). This meta-analysis showed that of the known modifiable risk factors for breast cancer, obesity (vs normal weight) had the highest risk (OR = 2.17, 95% CI 1.47 to 3.21; I(2) = 85.7) followed by age at marriage (25-29 vs < 18 years old) (OR = 2.00, 95% CI 1.53 to 2.61; I(2) = 0), second-hand smoking (OR = 1.86, 95% CI 1.58 to 2.19; I(2) = 0), smoking (OR = 1.83, 95% CI 1.41 to 2.38; I(2) = 18.9), abortion history (OR = 1.44, 95% CI 1.02 to 2.05; I(2) = 66.3), oral contraceptive use (OR = 1.35, 95% CI 1.11 to 1.63; I(2) = 74.1), age at marriage (18-24 vs