Firefighters are exposed to hot environments, which results in elevated core temperatures. Rapidly reducing core temperatures will likely increase safety as firefighters are redeployed to subsequent operational tasks. This study investigated the effectiveness of cold-water immersion (CWI) and iced-slush ingestion (SLUSH) to cool firefighters post-incident. Seventy-four Australian firefighters (mean ± SD age: 38.9 ± 9.0 years) undertook a simulated search and rescue task in a heat chamber (105 ± 5 °C). Testing involved two 20-min work cycles separated by a 10-min rest period. Ambient temperature during recovery periods was 19.3 ± 2.7 °C. Participants were randomly assigned one of three 15-min cooling protocols: (i) CWI, 15 °C to umbilicus; (ii) SLUSH, 7 g·kg−1 body weight; or (iii) seated rest (CONT). Core temperature and strength were measured pre- and postsimulation and directly after cooling. Mean temperatures for all groups reached 38.9 ± 0.9 °C at the conclusion of the second work task. Both CWI and SLUSH delivered cooling rates in excess of CONT (0.093 and 0.092 compared with 0.058 °C·min−1) and reduced temperatures to baseline measurements within the 15-min cooling period. Grip strength was not negatively impacted by either SLUSH or CONT. CWI and SLUSH provide evidence-based alternatives to passive recovery and forearm immersion protocols currently adopted by many fire services. To maximise the likelihood of adoption, we recommend SLUSH ingestion as a practical and effective cooling strategy for post-incident cooling of firefighters in temperate regions.