Breast cancer is the second most common malignancy among Korean women. The incidence of breast cancer has increased since 1999, which is when the national screening program involving mammography started. Until now, the benefits of screening mammography have been emphasized, but information about its benefits and harms should be provided in a comprehensive fashion, in order to guide people toward making informed decisions. Although the main benefit of screening is reduction of breast cancer mortality, harms such as overdiagnosis, overtreatment, false positive and false negative diagnoses, and radiation-induced breast cancer, can all occur as a result of screening. The 2015 Korean guideline for breast cancer screening recommends biennial screening mammography for asymptomatic women aged 40 to 69 years. This review discusses the benefits and harms of screening mammography in light of evidence-based approaches obtained from randomized trials, meta-analysis, and guidelines.