Numerous psychosocial variables influence students’ academic performance in secondary schools in the world and Kenya in particular. The psychosocial dynamics such as family supportiveness, school conduciveness and self-efficacy influence the learners’ life and consequently academic performance. Empirical evidence is lacking on the combined influence of family supportiveness, school conduciveness and self-efficacy on academic performance. The purpose of this study was to assess the perceived psychosocial dynamics and their influence on academic performance in secondary schools in Murang’a and Kirinyaga counties. The study was based on the systems theory and adopted correlational research design. Target population of the study was 5879 consisting of all form three students in extra-county and national schools in Murang’a and Kirinyaga counties. A stratified simple random sampling was used get a sample size of 412 respondents. Data was analysed using descriptive and inferential statistics. Results indicated that students in Kirinyaga county were more endowed psychosocially with a mean of 63.44% compared to their Murang’a counterparts with 59.74%, with a significant difference. The psychosocial dynamics correlated positively with academic performance with a calculated Pearson’s correlation coefficient r=0.339, with p-value=0.000<0.05. There was a positive association between family supportiveness, school conduciveness, self-efficacy and the overall psychosocial dynamics. However, the relationship between school conduciveness and academic performance was absolutely zero. The study recommended that the government should invest in further in the formation programs for teachers and cascade them to learners targeting to boost learners’ mindset, personal perception and psychosocial dynamics in the students.