Self-confidence in science enhances the pursuance of science-related fields. Low self-belief in students’ ability to perform in science subjects has been cited as a factor that has led to declined examination grades. Consequently, impeding admission of students in Murang’a County, into career courses that require science subjects. This study embarked on investigating students’ selfefficacy in science and career decisiveness among students in secondary schools in Murang’a County Kenya. The study explored the cognitive domain of the Social Cognitive Career Theory (SCCT). Correlations were established between the variables. A sample population of 498 form three students in public schools was derived by Cochran’s sample size formula. The sample included boys, girls, and coeducational schools, selected using purposive and proportionate sampling. The science self-efficacy scale and career decision scale (CDS) were utilized to collect data. Inferential data was analyzed by SPSS determining associations between the variables. Positive relationships were realized between low science self-efficacy and Career decision making. High science self-efficacy had a negative correlation with students’ ability to decide on a career option. The findings suggest the significance of science self-efficacy in stimulating students’ decisions in science.