Lymphedema is a debilitating complication following mastectomy, affecting the arm functions and quality of life (QOL) of breast cancer patients. Studies have shown the beneficial effects of upper-limb exercises on lymphedema in clinical settings. However, there is a dearth of evidence regarding the effect of home-based exercises on lymphedema; therefore, we examined the effect of a home-based exercise program on lymphedema and QOL in postmastectomy patients. Thirty-two female postmastectomy lymphedema patients participated in an individualized home-based exercise program for 8 weeks. Arm circumference, arm volume, and QOL (36-Item Short Form Health Survey) were measured before and after the program. Data were analyzed with the use of paired t-tests for circumferential and volumetric measures and Wilcoxon signed ranks tests for QOL. Significance level was set at p < 0.01 with Bonferroni correction (alpha/n = 0.05/5 = 0.01). Analysis showed a statistically significant improvement in the affected upper-limb circumference and volume (~122 mL reduction, p < 0.001) and in the QOL scores (p < 0.001) at the end of the home-based exercise program. The individualized home-based exercise program led to improvement in affected upper-limb volume and circumference and QOL of postmastectomy lymphedema patients.