Male involvement in maternal and child health is recognised as a valuable strategy to improve care-seeking and uptake of optimal home care practices for women and children in low- and middle-income settings. However, the specific mechanisms by which involving men can lead to observed behaviour change are not well substantiated. A qualitative study conducted to explore men’s and women’s experiences of male involvement interventions in Tanzania and Zimbabwe found that, for some women and men, the interventions had fostered more loving partner relationships. Both male and female participants identified these changes as profoundly meaningful and highly valued. Our findings illustrate key pathways by which male involvement interventions were able to improve couples' emotional relationships. Findings also indicate that these positive impacts on couple relationships can motivate and support men’s behaviour change, to improve care-seeking and home care practices. Men’s and women’s subjective experiences of partner relationships following male involvement interventions have not been well documented to date. Findings highlight the importance of increased love, happiness and emotional intimacy in couple relationships - both as a wellbeing outcome valued by men and women, and as a contributor to the effectiveness of male involvement interventions.