Coingestion of ketone salts, caffeine and the amino acids, taurine, and leucine improves endurance exercise performance. However, there is no study comparing this coingestion to the same nutrients without caffeine. We assessed whether ketone salts-caffeine-taurine-leucine (KCT) supplementation was superior to caffeine-free ketone salts-taurine-leucine supplementation (KT), or to an isoenergetic carbohydrate placebo (CHO-PLAC). Thirteen recreationally active men (mean ± SD: 177.5 ± 6.1 cm, 75.9 ± 4.6 kg, 23 ± 3 years, 12.0 ± 5.1% body fat) completed a best effort 20-km cycling time-trial, followed 15 min later by a Wingate power cycle test, after supplementing with either KCT (approximately 7 g of beta-hydroxybutyrate, approximately 120 mg of caffeine, 2.1 g of leucine, and 2.7 g of taurine), KT (i.e., same supplement without caffeine), or isoenergetic CHO-PLAC (11 g of dextrose). Blood ketones were elevated (p < .001) after ingestion of both KCT (0.65 ± 0.12 mmol/L) and KT (0.72 ± 0.31 mmol/L) relative to CHO-PLAC (0.06 ± 0.05 mmol/L). Moreover, KCT improved (p < .003) 20-km cycling time-trial performance (37.80 ± 2.28 min), compared with CHO-PLAC (39.40 ± 3.33 min) but not versus KT (38.75 ± 2.87 min; p < .09). 20-km cycling time-trial average power output was greater with KCT (power output = 180.5 ± 28.7 W) versus both KT (170.9 ± 31.7 W; p = .049) and CHO-PLAC (164.8 ± 34.7 W; p = .001). Wingate peak power output was also greater for both KCT (1,134 ± 137 W; p = .031) and KT (1,132 ± 128 W; p = .039) versus CHO-PLAC (1,068 ± 127 W). These data suggest that the observed improved exercise performance effects of this multi-ingredient supplement containing beta-hydroxybutyrate salts, taurine, and leucine are attributed partially to the addition of caffeine.