It has been argued that ambidexterity can be achieved by establishing strategic alliances with partners that occupy a downstream or upstream position in the innovation value chain (i.e., alliance ambidexterity), hence reconciling the tensions between exploration and exploitation. However, empirical tests confirming that this partnering strategy improves innovation performance are still scant. Therefore, in this paper, we aim at covering this gap by empirically analyzing the relationship between alliance ambidexterity and innovation performance. Furthermore, since firm age affects firms' commitment toward explorative and exploitative activities, we also examine the moderating effect of firm age on the abovementioned relationship. Results are based on a sample of 1017 biotechnology companies that have established, at least, one strategic alliance over the period 1982-2011. In detail, using a random-effects negative binomial regression, we find that alliance ambidexterity positively influences innovation performance, and firm age exerts a negative moderating effect.