The study examined family types and school types as determinants of in-school adolescents’ risky sexual behaviour in Yenagoa educational zone of Bayelsa State, Nigeria. The study adopted a correlational survey research design to determine between family types and school types as determinants of in-school adolescents’ risky sexual behaviour in Yenagoa educational zone of Bayelsa State, Nigeria. The population of the study consisted of thirty five (35) public secondary schools in Yenagoa educational zone of Bayelsa State, Nigeria with a total of eight thousand, nine hundred and thirty nine (8,939) SS1 and SS2 students. Twenty nine (29) private schools with a total of three thousand four hundred and eighty four (3,484) students in private secondary schools in Yenagoa educational zone of Bayelsa State, Nigeria. The simple random sampling technique was adopted to select five (5) public secondary schools and five private secondary schools in Yenagoa educational zone of Bayelsa State, Nigeria. The sample for the study consisted of forty (40) SS1 and SS2 students from five (5) selected public schools and five (5) selected private schools in Yenagoa educational zone of Bayelsa State, Nigeria with a total sample size of four hundred (400) in-school adolescents. A self-designed instrument titled family types and school types on adolescents sexual behaviour questionnaire (FTSTASBQ) was used to collect data for the study. The instrument was validated and yielded a reliability coefficient of 0.86. The research questions were analyzed using mean and standard deviation, while Spearman rank was adopted in analying the stated hypotheses. From the analysis, the study found out that family types and school types have significant relationship with adolescents’ risky sexual behaviour in Yenagoa educational zone, Bayelsa State.