We explored CS1 students' perceived instrumentality (PI) for the course and aspirations for a career related to CS. Perceived in-strumentality refers to the connection one sees between a current activity and a future goal. There are two types of PI: endogenous and exogenous. Endogenous instrumentality refers to the perception that mastering new information or skills is important for achieving distal goals. Exogenous instrumentality refers to the perception that obtaining an external reward (such as a grade) is essential for obtaining future goals. We investigated (1) how students' PI and career aspirations changed over the course of a semester, (2) how these changes differed as a function of course enrollment and major (CS or not), (3) the relationship between PI and career aspirations, and (4) whether PI and career aspirations predicted academic achievement. Overall and for most subgroups, exogenous instrumentality increased significantly and endogenous instrumentality decreased significantly across the semester, though the degree of change varied among some subgroups. Career aspirations decreased overall and for most subgroups, but CS majors showed a much smaller decrease than non-majors, and students in a CS/business honors course showed an overall increase in career aspirations. Finally, students' achievement out-comes were predicted by their PI and career aspirations. These findings contribute to the literature on motivation in CS1 courses and points to PI as a promising avenue for influencing student motivation. Implications for student motivation and retention in CS and other STEM courses are also discussed.