In the context of a couples cohort established to evaluate an optimised couples-focused behavioural intervention in rural South Africa, we examined: (1) Is couples’ relationship quality (RQ) associated with couples HIV testing and counselling (CHTC) uptake? (2) Does CHTC uptake or the intervention components uptake improve subsequent RQ? Enrolled couples, (n = 218), previously naïve to couples HIV testing, were invited to two group sessions and offered four couples counselling sessions (CS1-CS4), as part of the intervention and administered a questionnaire individually at baseline, four weeks, and four months, which included item-scales to measure RQ: satisfaction, intimacy, dyadic trust, conflict, and mutual constructive communication. Logistic models indicated that no baseline RQ measures were significantly associated with CHTC uptake. Linear regression models showed that CHTC uptake before four weeks assessment significantly improved couples’ satisfaction and trust at four weeks, and intimacy at four months. Attending at least one CS was associated with increased satisfaction, intimacy, and decreased conflict within couples at four weeks; the improvement in intimacy was sustained at four months. Consistent with the theoretical interdependence model, our findings suggest that CHTC and CS seemed to strengthen aspects of relationship quality, possibly leading to further collaboration in managing lifestyle changes and treatment adherence.