Abstract: Background: Pre-workout supplements containing numerous ingredients claim to increase performance and strength. Product-specific research is important for identifying efficacy of combined ingredients. The purpose of this study was to evaluate the effects of a proprietary pre-workout dietary supplement containing creatine monohydrate, beta-alanine, L-Tarurine, L-Leucine, and caffeine, on anaerobic power, muscular strength, body composition, and mood states. Methods: In a double-blind, randomized, matched-pair design, twenty male subjects (mean ± SD; 22.4 ± 9.5 yrs, 76.9 ± 11.2 kg, 22.7 ± 9.5% body fat), consumed either 30 g of a pre-workout supplement (SUP) or maltodextrin placebo (PLC) 30 minutes before a resistance training workout, after completing baseline testing. Body composition was determined via dual-energy x-ray absorptiometry (DEXA). Subjects completed 12 vertical jumps for height (VJ) and one repetition maximum (1RM) and repetitions to failure lifts on bench (BPM) and leg press (LPM). Finally, subjects completed a Wingate power test on a cycle ergometer [mean power (WMP) and peak power (WPP)]. After baseline testing, participants completed eight days of supplementation and four split-body resistance-training bouts. Side effect questionnaires were completed daily 30 minutes after consuming the supplement. Subjects completed post-supplement testing on Day 8. Data were analyzed utilizing a 2 × 2 repeated measures ANOVA [treatment (PLC vs SUP) × time (T1 vs T2)] and ninety-five percent confidence intervals. Results: There were no significant treatment × time interactions (p > 0.05). There were no significant changes in %body fat (%BF; Δ-0.43 ± 0.58; p = 0.920), fat mass (Δ-2.45 ± 5.72; p = 0.988), or lean body mass (LBM; 10.9 ± 12.2; p = 0.848). 95% CI demonstrated significant LBM increases for both groups. There was a main effect for time for WPP (Δ100.5 ± 42.7W; p = 0.001), BPM (Δ8.0 ± 12.9 lbs; p = 0.001), and LPM (Δ80.0 ± 28.8 lbs; p = 0.001), with no significant differences between treatments. There was no significant difference in mood states between groups or over time. Conclusion: The proprietary pre-workout blend combined with eight days of training did not significantly (ANOVA) improve body composition or performance. While not significant, greater gains in LPM were demonstrated in the SUP group for lean body mass and lower body strength. Future studies should evaluate more chronic effects of proprietary pre-workout blends on total training volume and performance outcomes.