BackgroundAlthough softball players are often required to play in hot environments, scarce evidence is available regarding the effects of ice slurry ingestion on body temperature and pitching performance in softball pitchers in a hot environment. Thus, this study investigated the effects of ice slurry ingestion before and between innings on body temperature and softball pitching performance in a hot environment.MethodsIn a randomized crossover design, seven heat-acclimatized amateur softball pitchers (four males and three females) completed simulated softball games consisting of 15 best-effort pitches per inning for seven innings with between-pitch rest intervals of 20 s. Participants were assigned to either a control trial (CON: ingestion of 5.0 g·kg−1of cool fluid [9.8 ± 2.2 °C] before simulated softball games and 1.25 g·kg−1of cool fluid between inning intervals) or an ice trial (ICE: ingestion of ice slurry [− 1.2 ± 0.1 °C] based on the same timings and doses as the CON). Participants performed both trials in an outdoor ground during the summer season (30.8 ± 2.7 °C, 57.0 ± 7.9% relative humidity).ResultsIce slurry ingestion before the simulated softball game (pre-cooling) resulted in a greater reduction in rectal temperature compared with cool fluid ingestion (p= 0.021,d= 0.68). No significant differences were observed between the trials in rectal temperature changes during the simulated softball game (p> 0.05). Compared to the CON, heart rate during the game was significantly decreased (p< 0.001,d= 0.43), and handgrip strength during the game was significantly increased (p= 0.001,d= 1.16) in the ICE. Ratings of perceived exertion, thermal comfort, and thermal sensation were improved in the ICE compared to those in the CON (p< 0.05). Ball velocity and pitching accuracy were not affected by ICE.ConclusionsIce slurry ingestion before and between innings reduced thermal, cardiovascular, and perceptual strain. However, it did not affect softball pitching performance compared to cool fluid ingestion.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40101-023-00329-0.