Background: Sexual concerns are distressing for breast cancer survivors and interfere with their intimate relationships. This study evaluates the efficacy of a four-session couple-based intervention delivered via telephone, called Intimacy Enhancement (IE). The IE intervention is grounded in social cognitive theory and integrates evidence-based techniques from cognitive behavioral couple therapy and sex therapy to address survivors’ sexual concerns and enhance their and their partners’ sexual, relationship, and psychological outcomes. Methods: This trial is designed to evaluate the efficacy of the IE intervention in improving survivors’ sexual function, the primary study outcome. Secondary outcomes include survivors’ sexual distress, partners’ sexual function, and survivors’ and partners’ relationship intimacy and quality as well as psychological distress (depressive symptoms and anxiety symptoms). Additional aims are to examine whether treatment effects on patient sexual function are mediated by sexual communication and self-efficacy for coping with sexual concerns and to explore whether survivor age and race/ethnicity moderate intervention effects on survivors’ sexual function. Eligible adult female breast cancer survivors reporting sexual concerns and their intimate partners are recruited from two academic sites in the USA and are randomized to either the IE intervention or to a control condition of equal length offering education and support around breast cancer-related health topics (Living Healthy Together). The target sample size is 120 couples. Self-report outcome measures are administered to participants in both conditions at baseline (T1), post-treatment (T2), 3 months post-treatment (T3), and 6 months post-treatment (T4). Discussion: Evidence-based interventions are needed to address sexual concerns for breast cancer survivors and to enhance their and their intimate partners’ sexual, relationship, and psychological well-being. This randomized controlled trial will allow us to examine the efficacy of a novel couple-based intervention delivered via telephone for breast cancer survivors experiencing sexual concerns and their intimate partners, in comparison with an attention control. Findings of this study could influence clinical care for women with breast cancer and inform theory guiding cancer-related sexual rehabilitation. Trial registration: ClinicalTrials.gov, NCT03930797. Registered on 24 April 2019.