Self-talk is a psychological skill that benefits motor performance by controlling and organizing performers' thoughts. While the behavioral effects of self-talk are clear, research on the mechanisms underpinning the effects of different modes of self-talk is sparse. To address this issue, we propose and test a psychophysiological model of the effects of self-talk on motor performance. Forty golf novices practiced a golf putting task while using either instructional or motivational self-talk preceding each putt. We measured performance (radial error), technique (club kinematics and muscle activity), cardiac activity (heart-rate and event-related heart-rate change), as well as electroencephalographic alpha power and connectivity in a randomized (group: instructional self-talk, motivational self-talk) experimental design. Instructional self-talk promoted superior technique and was associated with greater parietal alpha power and weaker connectivity between frontal and parietal electrodes and all other scalp sites, possibly indicative of increased top-down control of action. These findings provide initial evidence for an information-processing mechanism underlying the benefits of instructional self-talk. They also cast doubt on the validity of left-frontotemporal connectivity as a measure of verbal-analytic processing during motor tasks. Motivational self-talk led to increased heart-rate and reduced event-related heart rate variability, suggesting an effort-based mechanism to explain the benefits of motivational self-talk. Our study represents the most complete multi-measure investigation of self-talk to date. We hope that our psychophysiological model of self-talk will encourage researchers to move beyond the exclusive reliance on behavioral and self-report measures to discover the mechanisms underlying the benefits of self-talk for performance.