To date, mental fatigue has been shown to lead to a general decline in cognitive and motor control processing. The goal of the current research was to establish the impact of mental fatigue on the contribution of explicit (i.e., conscious strategy) and implicit (unconscious) processes to visuomotor adaptation. Participants were divided into a mental fatigue (MF) and control group. Mental fatigue was induced through a time load dual back task (TLDB), in which participants were required to respond as quickly as possible to digits displayed on the screen in a choice reaction time task, as well as respond to letters based on recall of previously presented letters. The TLDB task lasted for 32 minutes, and the control group watched a documentary for a similar length of time. Subjective feelings of mental fatigue, as indicated on a self-report questionnaire, demonstrated that mental fatigue was significantly higher for the MF group after completion of the TLDB task. There was no similar increase for the control group. The increased mental fatigue was associated with decreased visuomotor adaptation to a 40-degree cursor rotation, such that participants in the MF group adapted their reaches to a lesser extent both early and late in training compared to the control group. Furthermore, correlational analyses established that greater mental fatigue reported by participants was associated with less explicit adaptation and greater implicit adaptation. Taken together, these results suggest that mental fatigue decreases the ability to engage in explicit processing, limiting the overall extent of visuomotor adaptation achieved.