BACKGROUND: Male partner involvement (MPI) has been recognized as a priority area to be strengthened in Prevention of Mother to Child Transmission (PMTCT) of HIV. We explored the impact of Couple Oriented Counselling (COC) in MPI in sexual and reproductive health and associated factors. METHOD: From February 2009 to October 2011, pregnant women were enrolled at their first antenatal care visit (ANC-1) and followed up until 6 months after delivery in the Mother and Child Center of the Chantal Biya Foundation within the randomized prenahtest multicentric trial. The MPI index was defined using sexual and reproductive health behaviour variables by using multiple correspondence analysis followed by mixed classification. Men were considered as highly involved if they had shared their HIV test results with their partner, had discussed on HIV or condom used, had contributed financially to ANC, had accompanied their wife to ANC or had practiced safe sex. Factors associated to MPI were investigated by the logistic model with GEE estimation approach. RESULTS: A total of 484 pregnant women were enrolled. The median age of the women was 27 years (IQR: 23-31) and 55.23% had a gestational age greater than 16 weeks at ANC-1. Among them, HIV prevalence was 11.9% (95% CI: 9.0-15.4). The median duration of the women's relationship with their partner was 84 months (IQR: 48-120). MPI index at 6 months after delivery was significantly greater in the COC group than the classical counselling group (14.8% vs 8,82%; p = 0,043; Fig 1). The partners of the women who participated in the COC were more likely to be involved during follow up than others (aOR = 1.45; 95% CI = 1.00-2.10). Partners with no incoming activity (aOR = 2.90; 95% CI = 1.96-4.29), who did not used violence within the couple (aOR = 1.70; 95% CI = 1.07-2.68), and whose partner came early for ANC-1 (aOR = 1.37; 95% CI = 1.00-1.89) were more likely to be involved than others. CONCLUSION: MPI remains low in stable couples and COC improves partner involvement. Our findings also support the need of strengthening outreach towards "stable" couples and addressing barriers. This could go a long way to improve PMTCT outcomes in Cameroon.< Réduire