Breast cancer is the leading cause of cancer death worldwide and the second common cancer overall. Breast self-examination is one of the cheapest methods used for the early detection of breast cancer in asymptomatic women. However, the practice of breast self-examination remains low in Ethiopia. Therefore, this study aimed to assess breast self-examination practice and associated factors among women attending family planning services in Modjo public health facilities in southwest Ethiopia. Patient and Methods: Facility-based cross-sectional study was conducted in Modjo public health facilities from October 01, 2020, to October 30, 2020. Data were collected from 420 women by using an interviewer-administered structured questionnaire. Variables with a P-value ≤0.2 in the bivariate analysis were included in the multivariable logistic regression model. Results of regression analysis were shown as odds ratio (OR) and confidence intervals (95% CI).Results: Overall 86 (20.5%) of the participants had ever performed breast self-examination. The odds of breast self-examination practice among women with tertiary level of education were 2.14 [AOR: 2.14; 95% CI: (1.45, 6.74)] times higher compared to those with secondary education. Women who knew breast self-examination were 4.32 [AOR: 4.32; 95% CI: (1.81, 10.81)] times higher odds of breast self-examination practice compared to their counterparts. The odds of breast self-examination practice among women who had a positive attitude were 2.7 [AOR: 2.7; 95% CI: (1.03, 6.91)] times higher compared to women with a negative attitude towards breast self-examination. Conclusion: Breast self-examination practice was low within the study area. Tertiary level of education, having Knowledge on breast self-examination and a positive attitude towards breast self-examination were found to have a significant association with breast self-examination practice. Breast self-examination should be promoted by improving awareness and providing special health education for women that had low educational level.