Teen motherhood is a major concern in the world and a study by Lowen (2012), reported that United States of America leads in the rate of teen motherhood. In developing countries, the Sub-Saharan Africa has the highest number of teen mothers. According to the Centre for the Study of Adolescent Kenya, 13000 girls leave school every year due to teen pregnancy and motherhood. There are many teen mothers in secondary schools in Rarieda Sub-County. The purpose of this study was to investigate the influence of personality traits on social adjustment among secondary school re-admitted teen mothers in Rarieda Sub-County. The objectives of the study were: to investigate the influence of extroversive personality trait on social adjustment among re-admitted teen mothers in Rarieda Sub-County; to find out the influence of introversive personality trait on social adjustment among re-admitted teen mothers in secondary school learners in Rarieda Sub-County; to establish the influence of neuroticism personality trait on social adjustment among re-admitted teen mothers in secondary school learners in Rarieda Sub-County and to establish strategies for social adjustment among teen mothers. Eysenck‟s personality traits theory and Social comparison theory were used in this study. The study adopted a concurrent triangulation design. The study‟s target population of 217 consisted of all re-admitted teen mothers, 34 teacher counsellors and 34 deputy principals in the 34 day mixed secondary schools in Rarieda Sub-County. The sample size consisted of 149 teen mothers, 10 teacher counsellors and 10 deputy principals. Data collection tools were Eysenck personality questionnaire, social adjustment questionnaire and interview schedules. Saturated sampling technique was used to obtain the re-admitted teen mothers and purposive sampling technique was used to obtain 10 teacher counsellors and 10 deputy principals. Validity was ensured by the assistance of the two university supervisor‟s judgement while reliability was ensured by the internal consistency technique and Cronbach‟s coefficient of r =0.85 was reported. Quantitative data was analysed by Pearson correlation while qualitative data was analysed using thematic analysis. SPSS version 22 was used in the study. The study revealed a strong negative correlation of -0.889 between introversive personality traits on social adjustment among re-admitted team mothers; a weak positive correlation of 0.366 between neuroticism personality trait and social adjustment among re-admitted team mothers and a strong positive correlation of 0.742 between extroversive personality traits on social adjustment among re-admitted teen mothers. The study recommended that Ministry of Education should develop educational and social programmes that would increase the teen mothers‟ opportunity to experience success. Teacher Counsellors should adopt appropriate therapy techniques to assist the introverts and neurotic teen mothers adjust in school.