Australian Football (AF) is Australia's major football code. Despite research in other football codes, to date, no data has been published on the physiological responses of AF players during match play. Fifteen athletes (17.28 ± 0.76 yrs) participated in four pre-season matches, sanctioned by Australian Football League (AFL) Victoria, investigating Heart Rate (HR), Blood Lactate (BLa), Core Temperature (Tcore), and Hydration status. Match HR was measured continuously using HR monitors. BLa was measured via finger prick lancet at the end of each quarter of play. Tcore was measured by use of ingestible temperature sensor and measured wirelessly at the end of each quarter of play. Hydration status was measured using refractometry, measuring urine specific gravity, and body weight pre and post-match. Environmental conditions were measured continuously during matches. Results of HR responses showed a high exertion of players in the 85-95% maximum HR range. Elevated mean BLa levels, compared to rest, were observed in all players over the duration of the matches (p = 0.007). Mean Tcore rose 0.68 °C between start and end of matches. Mean USG increased between 0.008 g/ml (p = 0.001) with mean body weight decreasing 1.88 kg (p = 0.001). This study illustrates physiological responses in junior AF players playing in the heat as well as providing physiological data for consideration by AF coaching staff when developing specific training programs. Continued research should consider physiological measurements under varying environments, and at all playing levels of AF, to ascertain full physiological responses during AF matches. Key pointsSpecific conditioning sessions for junior athletes should include high intensity bouts; greater than 85% of heart rate maximum zone.Football anaerobic conditioning activities (e.g. sprint training) should be randomised throughout training sessions to replicate demands of the game (e.g. training in a fatigued state).Coaches and fitness staff should provide education and player management strategies for fluid replacement at key opportunities (pre-match, formal breaks and substation on and off the field) during matches.