Low uptake of human immunodeficiency virus (HIV) testing and involvement in multiple sexual partnerships among men in Nigeria are likely perpetuating HIV transmission. This quantitative, cross-sectional study investigates the associations between HIV testing uptake, sociodemographic variables, HIV knowledge, attitudes regarding safer sex negotiation, and multiple sexual partnerships, utilizing the health belief model (HBM) to provide a theoretical foundation. Secondary data are from the 2013 Nigeria Demographic and Health Survey (NDHS), with a national sample of 17,359 men aged 15–49 years obtained through a three-stage stratified random design. Using Chi-square tests and binary logistic regression, significant associations are found between sociodemographic attributes of men (age, place of residence, marital status, religion, wealth status, ethnicity, and educational attainment), uptake of HIV test, and attitude toward negotiating safer sex and multiple sexual partnerships (p < .05). No significant association is observed with HIV knowledge related to sexual network. A substantial higher proportion of middle age men (25–39 years) reported engaging in multiple sexual partnerships than that observed in younger (15–24 years) or older (≥ 40 years) men or in Hausa men; Muslim men were less likely to be involved in this type of partnerships. Unforeseen results show that men who ever tested for HIV were significantly more prone to having multiple partnerships than men not previously tested for HIV (adjusted OR = 1.79, p < 0.05). The findings imply that HIV testing services alone without integrated structured post-test counseling and follow-up services are not effective for modifying sustained risk behaviors such as multiple sexual partnerships among men in Nigeria.