Sleep is an essential biological requirement to sustain human life and a critical component for athletes. There has been a rising trend for poor sleep in the general population and the problem persists as well within the athletic population. Research has demonstrated numerous benefits of optimized sleep on athletic performance and athlete wellness. Further investigation of potential dietary strategies to improve self-perceived sleep quality is warranted. This study examined the differences in perceived sleep quality and wellness between a 3-week baseline period and after a 3-week supplementation period, in which participants consumed a dietary supplement containing fermented whey protein + galacto-oligosaccharides (GOS) + casein protein daily. Validated questionnaires, namely, Athens Insomnia Scale (AIS), Physical Health Questionnaire (PHX), Kessler-6 Mental Stress Scale (K6) were used to measure perceived sleep quality and wellness on Day 1, Day 22 and Day 43. Additionally, multiple 24-h dietary recalls (ASA24), and food quality using the validated Rapid Eating Assessments for Participants (REAP) questionnaire, were used to assess dietary patterns throughout the study, while exercise occurrence was tracked through a self-developed daily questionnaire. A total of 54 healthy active adults (age=18-35yrs) experiencing gastro-intestinal (GI) complaints were included in the trial, and 50 participants were included in the final analysis. Significantly lower AIS-8 total scores were found on Day 43 compared to Day 22 while controlled for Day 1 (Day 43: 4.36 ± 3.68 versus Day 22: 5.02 ± 4.11, F=4.379 (1, 50), p=0.042), while no differences were found for wellbeing (p≥ 0.180). Dietary intake, food quality and exercise frequency did not change over time (p≥0.080). These results suggested that a daily protein + GOS supplement was associated with a decrease in AIS-8 total scores suggesting improved perceived sleep quality among athletes after 3 weeks. A controlled research study should confirm these results in the future. More research is required to assess the effects of protein + prebiotic supplementation on sleep parameters among athletes.