The ministry of education in Kenya has an overall goal to provide access to all levels of education irrespective of the social-economic status. Many recent research studies indicate that more girls have enrolled at all level of education for instance in the year 2001/2002 female enrolment at primary school level nationally was 49.3 percent of the whole population, 47.2 percent at secondary level and 32.2 percent at tertiary college. These findings show that transition rate of female decrease at each higher level of education. This study sought to investigate the influence of social determinants of transition rate of girls from primary to secondary education in Koibatek sub-county, Kenya. The study employed concurrent triangulation research design and targeted 91 head teachers and 2208 pupils. Simple random sampling was used to select 74 head teachers and 327 pupils. The study employed mixed methods approach. The data was collected using questionnaires and interviews. To ascertain the validity of research instrument, the researcher consulted experts and included their comments on instrument before data collection. To determine reliability of research instrument was piloted and a reliability coefficient calculated. A Reliability coefficient of 0.72 was obtained indicating that the instruments were reliable. To ascertain credibility and dependability of qualitative data the investigator certified that each respond in the research was reported in detail to allow an external investigator to repeat and achieve similar findings. Data was analysed using percentages, means and mode. In addition, Pearson Correlation analysis was used to test the study hypothesis. The study findings showed that 89.4% of the pupils believed that the involvement of girls in household chores at home influenced negatively their education. The study further found a significant and positive association (r = .807; p = .008) between social determinants and girls transition to secondary education The findings of the study will provide planners, policy makers and administrators with better understanding of the nature and determinants of transition rate and assist in the ongoing search for access and efficiency in education, it will also provide a base for further research on transition rate to other educational levels.