This study investigated the effect of sodium bicarbonate (NaHCO3–) ingestion on the Yo-Yo intermittent recovery test 1 (IR1). We tested the hypothesis that acute ingestion of NaHCO3 – would increase blood lactate concentrations [BLa], enhance performance, and reduce rating of perceived exertion (RPE) in the Yo-Yo IR1. Eight recreationally active males (N=8, age: 26±4 yr, height: 178±6 cm, body mass: 82±10 kg) participated in the Yo-Yo IR1 on two separate occasions, separated by 1 wk, in a randomized crossover design. Following familiarization, during seated rest, participants’ pretest [BLa] was taken, and participants then consumed either a placebo of 0.3 g·kg–1 body weight sodium chloride or 0.3 g·kg–1 body weight NaHCO3–. Sixty minutes postingestion, a standardized warm-up preceded the Yo-Yo IR1. Upon completion, postexercise [BLa] (mmol·L–1), RPE (arbitrary units) and Yo-Yo IR1 time to fatigue (s) were recorded. Paired T-test revealed a small but significant improvement in Yo-Yo IR1 performance under the NaHCO3 – condition (610±267 sec), compared to the placebo condition (556±259 sec; p=0.01; Cohen’s d=0.20). [BLa] increased more under the NaHCO3 – condition (1.6±0.7 to 17.5±5.2 mmol·L–1; p<0.001; Cohen’s d=4.29), compared to the placebo condition (2.0±0.7 to 11.5±5.0 mmol·L–1; p=0.001; Cohen’s d=2.66). Postexercise RPE was not significantly different between conditions. The results of this study suggest that acute NaHCO3– ingestion improves Yo-Yo IR1 performance without altering RPE, likely through an increased lactate efflux, demonstrated by increased [BLa].