Introduction: An important aspect of success in a HIV Prevention program is the effectiveness of interventions to reduce HIV transmission between serodiscordant couples. This study aims to explore the understanding and practice of positive prevention including condom use, sexually transmitted infections (STIs), opportunistic infections (OIs) and treatment seeking behavior for STIs and OIs among serodiscordant couples in Karnataka, south India. Materials and Methods: A cross sectional survey, was conducted among 326 serodiscordant couples in Haveri and Chitradurga Districts located in central part of Karnataka, between January 2014 to May 2015. Participants were selected using a simple random sampling technique and were recruited with the help of peer groups while seeking care and support services. Index people living with HIV (PLHIVs) were interviewed with the help of a pretested structured interview schedule. Data was analysed by calculating mean, standard deviations and proportions. The tests of significance applied were Chi-square test. A P-value of 0.05 was considered to be statistically significant Results: 99.4% believe that condoms can protect them from STIs whereas only 80.4% (81.7% of men & 74% of women) reported that they use condoms with spouse. PLHIV in the younger age group (21-30 years) reported higher condom use with their spouse when compared to middle (31-40 years) and older (>40 years) age groups. 80.8% (79% of men & 90% of women) of participants had good knowledge on STIs. Those with good knowledge on STI reported higher rates of condom use with spouse (81.7%) and reported lesser STI episodes, while compared to others. 21.4% of PLHIV who have adopted permanent methods of contraception reported not using condoms with spouse. Education of Index PLHIV, spousal education and enrollment with support groups were found to be positively associated with higher condom use with spouse, lower incidence of STIs and OIs. Conclusions: Gaps exist in translation of knowledge into practice. Low levels of condom use among middle aged couples and those who have adopted permanent methods of contraception, is a cause for concern and calls for further investigation of other structural and social barriers to condom use among these population groups.