Agentic engagement, or attempts to proactively influence instruction, predicts positive classroom climate and students' motivation. As such, it is a potentially effective target for intervention, though causal evidence is limited. This investigation explored whether an agentic orientation could be cultivated through a brief, online intervention for university students and the potential benefits of such an intervention. Three randomized field experiments with college students in psychology (Study 1 and Study 2) or introductory physics and chemistry courses (Study 3) tested the effects of an agentic orientation intervention compared with an alternative study skills intervention or an inactive control condition. The intervention encouraged students to view their motivational experiences in class as malleable and responsive to agentic behaviors they were encouraged to use. Relative to the alternative intervention (Studies 1 and 3) and inactive control (Studies 1, 2, and 3), students exposed to the target intervention at the beginning of the semester later reported a more agentic mindset. Indirect effects indicated that the intervention predicted greater student-reported in-class agentic and other forms of engagement, instructor autonomy support, need satisfaction, domain personal interest, and intention to persist in the field at the end of the semester via an enhanced agentic mindset. Multigroup comparisons suggested that the intervention worked similarly for students who have been traditionally underrepresented in science compared with their counterparts, with limited evidence of variation on certain outcomes. The investigation provides preliminary causal evidence regarding the benefits of intervening on an agentic orientation.