The 21st Century work environment requires workers to have requisite soft skills and many organizations offer internship opportunities to enable students gain these skills and prepare them to function in current workplace. This study aimed to evaluate selected internship factors on mastery of soft skills among interns in the County Government of Nakuru. The specific objectives of the study are to analyse the effect of assessment criteria, competency of internship supervisors, person role fitness and institutional support on soft skills mastery among interns in Nakuru County Government. The study was anchored on experiential learning theory and Dreyfus model. The study adopted a descriptive research design. The population of the study was the 1300 interns stationed in the Nakuru County Government during the month of August from which a sample of 102 interns was obtained using stratified random sampling technique and a structured self-administered questionnaire was used to collect data. A pilot study was conducted in Baringo County, Mogotio Sub-county to ascertain the validity and reliability of the research instrument. Statistical Package for Social Sciences (SPSS) was used to analyze the data to obtain both descriptive and inferential statistics. The main descriptive statistics obtain were frequencies, percentages, means and standard deviation. Inferential statistics employed were Pearson‟s product moment correlation which helped to compute the direction and strength of the linear associations. Simple and multiple regression analysis were used to test the association between the variables. The study found out that assessment criteria significantly (β=0.772, Sig.