Objective: This study was aimed at assessing the longitudinal strain changes of RV function using three-dimensional speckle tracking echocardiography (3D STE) in breast cancer patients receiving anthracycline chemotherapy. Patients and Methods: A total of 95 women with breast cancer receiving epirubicin (360 mg/m 2) underwent 3D STE at baseline, the end of chemotherapy and 12 months after chemotherapy. 3D STE assessment included RV ejection fraction (EF), LV global longitudinal strain (GLS), RV GLS, and RV free wall longitudinal strain (RV FWLS). Meanwhile, serum hs-cTnI and NT-proBNP were measured. Chemotherapy-related cardiac dysfunction (CTRCD) was defined as an absolute decrease in 3D LVEF > 10% to a value <50%, while a percent reduction of 3D LV GLS > 15% indicated subclinical CTRCD. Results: Subclinical CTRCD occurred in 10 (10.5%) patients during follow-up. Compared to baseline, the 3D GLS of LV and GLS and FWLS of RV decreased significantly at 12months after chemotherapy (all p<0.01). Variations of 3D RV GLS and RV FWLS had a good discrimination for predicting subclinical CTRCD. The variation of 3D RV FWLS was the only independent predictor of subclinical CTRCD (OR, 1.37; 95% CI, 1.12-2.87; p = 0.028) in multivariate analysis. The cutoff value with −17.5% of 3D RV FWLS variation had a high predictive accuracy for subclinical CTRCD, with an AUC of 0.74, 80.5% sensitivity and 65.8% specificity. The association between 3D RV FWLS and the cumulative dose of anthracyclines was calculated by Spearman's test (r = −0.71, p < 0.001). Conclusion: Longitudinal strain analysis by 3D STE allows the identification of subclinical RV dysfunction when conventional indices of RV function are unaffected. 3D RV FWLS was superior to other parameters in early detection of the development of CTRCD in breast cancer patients receiving epirubicin therapy.