OBJECTIVE This study evaluated the effects of web-based interventions on anxiety and depression in patients with breast cancer by conducting a meta-analysis of relevant randomized controlled trials (RCTs). METHODS We searched the PubMed, Web of Science, Cochrane Library, Cumulated Index to Nursing and Allied Health Literature, Embase, and PsycINFO databases from their inception to January 5, 2024. When substantial heterogeneity was observed among the studies, a random-effects model was applied to calculate effect sizes in terms of the standardized mean difference (SMD) and assessed the quality of the included studies using the updated Cochrane risk-of-bias tool for RCTs. RESULTS Fourteen RCTs were included in this study. The meta-analysis indicated that web-based intervention alleviated anxiety (SMD = -0.26, 95% CI = -0.44 to -0.07, p < 0.01, I2 = 68%) and depression (SMD = -0.15, 95% CI = -0.25 to -0.06, p = 0.19, I2 = 26%) in patients with breast cancer. There was substantial heterogeneity in anxiety, and the analysis of potential causes revealed that the intervention method was a factor influencing the variability in the actual effect size. CONCLUSIONS This study showed that web-based interventions may help reduce anxiety and depression in patients with breast cancer. It also suggested the potential of these interventions as a strategy for alleviating symptoms in non-face-to-face settings. However, the limited number of studies and high heterogeneity in the subgroup analysis made it difficult to assess the effects of different intervention methods. Further high-quality research is needed to provide more reliable data on the effectiveness of various intervention methods.