This study examined the effectiveness of an applied mental skills training (MST) intervention utilizing mental skills to enhance intrinsic sources of enjoyment (ISOEs) as a means of promoting self-confidence, motivational style, and athletic performance, while also decreasing trait anxiety. The intervention project was designed to increase intrinsic SOE using a systematic and individualized mental training protocol, and then examine its relationships to mental skills and soccer performance. A Division 1 collegiate women’s soccer team was randomly assigned to treatment (n = 8) and control (n = 11) groups, equally distributed by academic year, position, and pre-season coach-evaluated starters and non-starts. Results revealed that the MST intervention significantly increased intrinsic enjoyment targeted psychological and competitive outcomes, both in practice and competition within the treatment group as compared to the control group. This study’s support for the impact mental skills training may have had on ISOEs, as well as other psychosocial outcomes and athletic performance can serve to highlight a mental skill often overlooked by consultants and coaches.