An experimental study has been conducted in order to investigate the relation between the slopes of wind-driven waves at short fetches and microscale breaking occurrence on the enhancement of oxygen transfer rate in a water body. A wind tunnel facility, containing a small water tank two meters long was utilized. Time series of the elevation and slope of the waves were recorded at three different fetches along the tank using a differential capacitance wave gauge and a high-velocity video camera. Captured images were qualitatively analyzed in order to identify wave states, with special interest on microbreaking phenomena. Oxygen transfer rate was obtained monitoring dissolved oxygen concentration after initial deoxygenation. A strong enhancement of wave slope and oxygen transfer rate at the transition to wave field with microscale breaking characteristics was observed. The transfer rate showed a linear relation with the mean square slope of the waves and was consistent with results from several previous publications at longer fetches.