The overall aim of this study was to measure the physiological responses of firefighters from a single fire service during simulated functional firefighting tasks and to establish the relationship between physical fitness parameters and task performance. 46 males and 3 females firefighters were recruited. Firefighters’ aerobic capacity levels were estimated using the Modified Canadian Aerobic Fitness Test (mCAFT). Grip strength levels, as a measure of upper body strength levels, were assessed using a calibrated J-Tech dynamometer. The National Institute for Occupational Safety and Health (NIOSH) protocol for the static floor lifting test was used to quantify lower body strength levels. Firefighters then performed two simulated tasks: a hose drag task and a stair climb with a high-rise pack tasks. Pearson’s correlation coefficients () were calculated between firefighters’ physical fitness parameters and task completion times. Two separate multivariable enter regression analyses were carried out to determine the predictive abilities of age, sex, muscle strength, and resting heart rate on task completion times. Our results displayed that near maximal heart rates of ≥88% of heart rate maximum were recorded during the two tasks. Correlation () ranged from −0.30 to 0.20. For the hose drag task, cardiorespiratory fitness and right grip strength (kg) demonstrated the highest correlations of −0.30 and −0.25, respectively. In predicting hose drag completion times, age and right grip strength scores were shown to be the statistically significant () independent variables in our regression model. In predicting stair climb completion times, age and NIOSH scores were shown to be the statistically significant () independent variables in our regression model. In conclusion, the hose drag and stair climb tasks were identified as physiological demanding tasks. Age, sex, resting heart rate, and upper body/lower body strength levels had similar predictive values on hose drag and stair climb completion times.