Educationists have observed that candidates’ summative scores in their exams correlates strongly with their continuous assessment’s tests in their former classes. They allege that although early sexual debut may not be a direct course of poor academic performance, higher educational aspiration is associated with postponement of sexually related activities. This study sought to determine the degree to which exposure to pre-marital sex activities influences academic achievements of secondary school pupils in Kakamega Central Sub-County. The study employed Psychosocial Theory of Personality development to support its findings. It adopted an ex-post facto research design to collect both quantitative and the qualitative data. A total of 4073 respondents consisting of 28 principals, 28 Heads of Department Guidance and Counseling and 4017 students participated. It used purposive sampling to select 28 principals and 28 Heads of Guidance and Counseling while Yamane (1967) formular was used to select 364 learners who were stratified according to their school populations. Questionnaires, Interview Schedules were used as research instruments. Half - split - half technique was used to test reliability of the instrument’s items on the questionnaire to yield a Cronbach’s alfa value of r = 0.85. Quantitative data was presented in frequency counts. Regression analysis tested relationship at 0.05 precision level. The results showed that Pornography from You Tube influenced academic performance by 53.2% (r = .532, P= .038); Pornographic literature and pictures by 41.0% (r = .410, P= .003) while soap operas influence was 50.8% (r = .508, P= .001). The study concluded that the most influential Internet Pornography that affect academic achievements of secondary schools’ students in Kakamega Central Sub-County are googled from You Tube followed by soap operas and Pornographic literature and pictures in that order. It was recommended that the government and parents be asked to participate in the efforts to block, prevent and advive learners on influences of sex related activities found online.