Student socio-economic factors influencing enrolment in Universities. University education plays a key role in the economic development of a country. In this respect, the government of Kenya has endeavored to increase enrolment in University education since independence. It has expanded opportunities at the University level and increased the chances of getting University admission through private self-sponsored programme. Nevertheless, it is a fact that people’s aspirations and ability to enroll in various programmes is sometimes limited by socio-economic factors. The purpose of the study was to determine the socio-economic factors influencing enrolment of undergraduate s self-sponsored students in Kisii University. The study was guided by the following objectives: To determine the influence of Parental level of education, Parental Occupation ,Parental Income and Birth order and Family size on enrollment of undergraduate self-sponsored students in Kisii University The study adopted a descriptive survey design. The target population was 1714.It consisted of a dean of students, an academic registrar and 1712 students of the 2013/2014 academic year cohort. The researcher used purposive sampling technique to select a dean of students and an academic registrar. Stratified random sampling technique was used to sample 513 students whowere 30% of the student target population. The instruments for data collection were questionnaires, in-depth interview and document analysis. Validity of instruments was determined by two experts in the Faculty of Education at Kisii University. Data was analyzed using both quantitative and qualitative methods. Reliability of the instruments was determined by piloting on the 2012/13 academic year cohorts. Piloting was done in five Faculties through test-retest method. Pearson Correlation was used to calculate reliability which was established at 0.741.Quantitative data was analyzed by use of descriptive statistics such as means, frequencies and graphs while qualitative data was analyzed on the basis of themes and sub themes. The researcher upheld the research ethics by ensuring the autonomy of the respondents. From the study, it was established that the most significant socio-economic factors influencing enrolment of undergraduate self-sponsored students were: nature of school attended, parental occupation education and income. The University socioeconomic factors that influenced enrolment were mostly the cost of the courses, financial support through bursaries, physical infrastructure, teaching staff, accessibility of the material required for the course and management. The conclusion was that socio-economic factors and gender constitute a significant determinant to undergraduate students’ enrolment. It was recommended that the government should endeavor to cushion the needy students pursuing their degrees through self-sponsored programme. A study should be carried out on financing of University education and participation of undergraduate students at Kisii University. Keywords: Kisii University, socio-economic factors, self-sponsored programme