This study investigated Turkish school students' attitudes towards STEM disciplines and careers and explored determinants of students' STEM career goals. In total, 117 lower secondary school students (aged 11 to 14) completed the "STEM Semantic Survey" including an open-ended question about their career intention after high school and the reasons for their goals. Using the conceptualisation of the influences of behavioural, personal, and contextual variables in career choice decisions, the students' descriptions of career goal reasons were presented to elaborate on the variables that influence their STEM career goals. Attitudes towards individual STEM disciplines were from moderate to high and towards STEM careers were high. The gender difference was negligible. One of the key determinants of students' career intentions was interests, involving interest in a particular career (e.g., architect) and career-relevant activities (e.g., planning, drawing, and designing) or subjects (e.g., mathematics). Larger, societal influences (altruism and patriotism) were among the motives of students' career goals. Implications for research, practice, and policymaking were presented.