Contextual interference (CI)—the practice of tasks in a random rather than blocked order—is known to impair immediate performance while enhancing long-term learning and transfer. In simple aiming tasks, CI has been shown to improve movement accuracy. However, whether these greater improvements extend to unpracticed parameters, such as novel distances or the contralateral hand—a relationship informed by schema theory—remains unexplored. Additionally, in non-sequential tasks, CI has been shown to affect processes that are preprogrammed before movement initiation, leaving reaction time and speed unaffected, yet this has not been empirically tested in simple aiming tasks. To address these gaps, we trained thirty-six participants over nine sessions on a computer-based aiming task involving three target distances. Participants were assigned to either a High Contextual Interference (HCI) group, practicing distances in random order, or a Low Contextual Interference (LCI) group, practicing in a blocked order. Performance was assessed in pretest, posttest, and retention sessions under both conditions, with evaluations extending to untrained parameters, including new distances and the contralateral hand. Despite reduced accuracy during training, the HCI group demonstrated significantly higher accuracy in retention and transfer tests compared to the LCI group across both trained and untrained parameters. Consistent with our hypothesis, no differences were observed in reaction time or movement speed, supporting that in simple aiming tasks, CI primarily affects pre-movement initiation processes. These findings confirm the robustness of CI effects in parameterization learning and extend its benefits to unpracticed motor parameters in simple aiming tasks.