This study evaluated changes in markers of acid-base balance that occurred during simulated soccer match-play. Sixteen academy soccer players participated in a soccer match simulation (SMS) that consisted of 90 min of soccer-specific exercise with skills throughout. Blood samples were obtained before exercise (pre-exercise), and every 15-min during the simulation (15, 30, 45, 60, 75 and 90-min), and 10 min into the half-time break (half-time). Blood lactate concentrations were elevated throughout exercise (Pre-exercise: 1.5 +/- 0.12 mmol[middle dot]L-1; 90 min: 6.1 +/- 0.7 mmol[middle dot]L-1, time effect: P<0.01, partial-eta2 = 0.740). Relative to pre-exercise values, actual blood bicarbonate (Pre-exercise: 28.02 +/- 0.92 mmol[middle dot]L-1; 90 min: 21.73 +/- 0.65 mmol[middle dot]L-1, time effect = P<0.01, partial-eta2 = 0.680), standard blood bicarbonate (Pre-exercise: 25.97 +/- 0.43 mmol[middle dot]L-1; 90 min: 22.87 +/- 0.31 mmol[middle dot]L-1, time effect = P<0.01, partial-eta2 = 0.667), base excess (Pre-exercise: 2.40 +/- 0.54 mmol[middle dot]L-1, 90 min: -1.57 +/- 0.39 mmol[middle dot]L-1, time effect = P<0.01, partial-eta2 = 0.664) and pH (Pre-exercise: 7.44 +/- 0.01 units; 90 min: 7.39 +/- 0.01 units, time effect = P<0.01, partial-eta2 = 0.542) were depressed throughout exercise. Interestingly, blood bicarbonate, base excess and pH recovered at half-time (P>0.05). This is the first study to provide data concerning the acid-base balance of familiarized soccer players during exercise that simulates soccer match-play. These findings suggest that: (1) blood pH is reduced during soccer-specific exercise, and (2) although buffering capacity is reduced throughout exercise, it returns to normal during half-time. Further research is warranted to develop interventions that can maintain acid-base balance throughout the full duration of a soccer match.