Background: Breast cancer (BC) is a major public health problem worldwide. Considering the high prevalence and mortality of BC in postmenopausal women, and since the population of Iran is aging, this study aimed to investigate the knowledge and attitude of postmenopausal women in Jahrom, Iran regarding BC screening. Methods: This cross-sectional study was performed on postmenopausal women referred to Honari Clinic of Jahrom in 2019. To select the samples, 120 women were randomly selected from the existing medical files. Data collection tools included a demographic information questionnaire and the knowledge and attitude questionnaire on BC screening behavior. After explaining the objectives of the research to the participants and obtaining a consent form, the questionnaire was answered by them. The data were entered into SPSS software version 21 and tested by descriptive statistics, chi-square, Kruskal-Wallis, and one-way ANOVA tests. Descriptive statistics were used to examine demographic data. Results: The level of knowledge of most participants (49.2%) was moderate, and the majority of them (94.2%) had a positive attitude. There was a significant association between the mean score of knowledge and attitude in postmenopausal women with source of information (P = 0.004). Most information came from radio and television, physician, health system staff, and friends and relatives. There was no significant association between the mean score of knowledge and attitude of postmenopausal women with breast-related diseases and family history of BC. Conclusions: The mass media, especially radio and television, as well as physician and health system staff, play an important role in raising women's awareness to increase their participation in BC screening programs.