Background: We examined the effects of ingesting two preworkout supplements (PWSs) on selective attention and response inhibition, perceived exercise readiness (herein, readiness), and exercise performance-related parameters. Methods: Resistance-trained participants (N = 19) were randomized to a double-blind, crossover (7-day washout) placebo (PLA)-controlled study supplementing with (1) PLA; (2) PWS [beta-alanine (3.2 g), arginine alpha ketoglutarate (2.0 g), creatine nitrate (2.0 g), ascorbic acid (500 mg), N-acetyl tyrosine (300 mg), caffeine (300 mg), tetramethyluric acid (10 mg), Mucuna pruriens extract standardized for 15% l-Dopa (1.0 g), theacrine (10 mg), pyridoxal 5-phosphate (1.48 mg), folic acid (0.50 mg), and methylcobalamin (1.8 mg)]; and (3) PWS150 at ∼150% the PWS dose. Primary outcomes were Stroop test responses for congruent, incongruent, and interference tasks. Secondary outcomes were readiness and exercise performance (bench and leg press/Wingate). Data were analyzed by general linear models and presented as mean (standard deviation) or mean change [95% confidence interval, CI]. Results: Significant improvements in Stroop word testing were observed for PWS (6.57, 95% CI [1.36–11.8]) and PWS150 (11.5, 95% CI [6.26–16.6]), but not PLA (1.31, 95% CI [−3.89 to 6.52]). Significant changes in Stroop color testing were observed for PWS150 (8.1, 95% CI [4.52–11.6]) and PLA (4.47, 95% CI [0.89–8.05]), but not PWS (2.31, 95% CI [−1.26 to 5.89]). Similar results were observed for word–color. When all domains were summed, PWS150 (27.42 counts, 95% CI [16.08–38.76]) and PWS (12.26 counts, 95% CI [0.92–23.60]) showed significant improvements, but not PLA (11.26 counts, 95% CI [−0.077 to 22.60]). No significant changes in readiness, exercise performance, or adverse changes were otherwise observed. Conclusion: Consistent improvements in selective attention and response inhibition were observed with PWS150, but not readiness or exercise performance.