This study assessed the knowledge of sexually transmitted infection among secondary school students in Ogba/Egbema/Ndoni Local Government Area of Rivers State. Five research questions and four hypotheses guide the study. The cross-sectional survey design was adopted for the study. A structured questionnaire with a reliability co-efficient 0.81 was used for data collection. Data was analysed using percentages and chi-square. The result showed that the knowledge of sexually transmitted infection among secondary school students in ONELGA was high as majority 370(93.0%) have ever heard about STIs. The types of STIs known to the respondents were gonorrhea 387(97.2%), syphilis 388(97.5%), HIV/AIDS 398(100%), Hepatitis B 365(91.7%), Chlamydia 363(91.5%) and Herpes 364(91.5%). Majority 390(98.0%) knew that sexual intercourse is the transmission route of STIs. There was no significant influence of gender and age on student’s knowledge of sexually transmitted infection among secondary school students in Ogba/Egbema/Ndoni Local Government Area of Rivers State (p>0.05). It was recommended among others that health educators should mobilize resources and take measures to improve young people’s awareness and knowledge about STIs prevention through educational training and guidance to maintain active and healthy lives.