As part of a larger, randomized controlled trial, we evaluated longitudinally the sexual functioning and relationship satisfaction of 69 partners of breast cancer (BC) survivors who received Internet-based cognitive behavioral therapy (CBT) for sexual dysfunction. The findings suggest that Internet-based CBT positively affects the partners' immediate post-CBT and longer-term overall sexual satisfaction, sexual intimacy, and sexual relationship satisfaction. No sustained changes in other areas of sexual functioning were observed. Our CBT program was focused primarily on the sexual health of the BC survivors. We recommend that future programs include more psychoeducational and behavioral elements targeted at the partners.