Background: Internet use has become pervasive in the society and has facilitated unrestricted access to sexual images and videos. Studies have discussed the social and psychological issues associated with this behaviour, especially among youths. However, there is paucity of studies on the prevalence of internet pornography viewing in Nigeria, the socio-demographic determinants of the behaviour, and its psycho-social effects on Nigerian youths. This study examined pornography viewing, socio-demographic determinants of the behaviour, and mental health of viewers.
 Methods: The study adopted a cross-sectional descriptive survey design and a multistage sampling technique. The study was conducted among undergraduate students of two tertiary institutions in Ogun State Nigeria. Three hundred and fifty (350) copies of questionnaires were administered. Data were collected on internet utilization, prevalence of pornography viewing, and mental health of viewers. Data were analysed through descriptive statistics for categorical data and chi-square test of independence. Basic ethical principles were adhered to.
 Results: The prevalence rate of internet pornography viewing was 82.93%. There were significant relationships between gender, marital status and pornography viewing (p<0.05) as pornography viewing was higher among males (80%) than females (32%) and higher among engaged (68%), single (65%) than married (18.5%). Majority of the respondents (60%) complained about their mental health.
 Conclusion: Internet pornography utilization is endemic among youths in Ogun state Nigeria as both males and females patronize internet pornography sites. Pornography viewing also has mental health implication on youths in Ogun State Nigeria. The findings of this study suggest the need for public sensitization among youths about the risks associated pornography viewing.