In infrastructure project practice, balancing and maximizing the combined effect of exploratory and exploitative innovation have attracted increasing attention, but it is still unclear how to foster ambidextrous innovation in infrastructure projects. To address this gap, we draw on the differentiation–integration framework of ambidexterity theory to deconstruct tactics for fostering ambidextrous innovation in infrastructure projects. A total of 313 observations were collected from infrastructure under construction, and the path hypotheses were tested by hierarchical regression. The findings suggest that in infrastructure projects, task conflict and expertise integration of diverse cross-functional teams provide powerful and complementary tactics for fostering ambidextrous innovation. The moderating effect of team autonomy support on the impact of team diversity on differentiation and integration tactics presents three different results. This study not only enriches the literature on how to foster ambidextrous innovation in infrastructure projects but also expands the ambidexterity research at the cross-functional team level and in infrastructure project contexts.