This study investigated the determinants of selection of A-level subjects‟ combination for future career choice among private secondary school students. The study was guided by the following specific objectives, to establish how personal interest determine the selection of A-level subjects combination for future career choice, to determine whether parents‟ economic status influences the selection of A-level subject combination for future career choice, to determine how parents level of education contributes to the selection of A-level subject combination for future career choice, to find out whether peer pressure determines the selection A-level subject combinations for future career choice. The study was guided by Self- Concept Theory of Career Choice and Development as well as Social Cognitive Career Theory. The study employed mixed research approach whereby the researcher used both qualitative and quantitative research approaches. Also, convergent parallel research design was used to guide the researcher from the data collection, data recording and data presentation. The researcher used questionnaires to get information from teachers and students while the heads of schools were interviewed. The researcher used both probability sampling and non-probability to get the sample size from the population. Lastly, the researcher conducted a pilot study to one of the secondary schools in Dodoma City Council before the real study so as to test the reliability of the research instruments. After testing the reliability of research instruments the researcher observed some weaknesses, therefore, the researcher made some corrections to make the instruments reliable to collect what were supposed to be collected from the respondents to help the researcher to write the report. The following are the findings are of this study, parents have a big influence on their children‟s selection of subject combinations, also teachers guide students according to their performance to select their subject combination. This study recommends that education must be provided to academic teachers and also students on selection of subject combination because this ensures right choice of A-level subjects' combination for future career choice.