PurposeWhile the performance benefits of relational resources and managerial ambidexterity have been widely discussed in coopetition literature, there is only limited evidence that illustrates the underlying relationships between these relational resources and managerial ambidexterity. Against this background, this paper aims to investigate how managerial ambidexterity moderates the innovation ambidexterity effects of relational resources (i.e. reciprocal investments and complementary resources).Design/methodology/approachThis study forwards various hypotheses that are grounded within the theoretical tenets of the relational view and the dynamic capabilities perspective. To test the hypotheses, this study uses survey data provided by 313 firms that pursue horizontal coopetition relationships.FindingsThe research findings offer important insights in that while reciprocal investments lead to innovation ambidexterity, complementary resources do not result in such benefits. Additionally, managerial ambidexterity complements the relational resources to develop innovation ambidexterity if and only if both managerial exploration and exploitation are applied simultaneously.Originality/valueAs opposed to widely-held beliefs, this study finds that firms' use of complementary resources is not likely to lead to innovation ambidexterity even though such resources can help in developing strong relationships. In addition, although often overlooked, managerial ambidexterity plays a vital role in transforming relational resources into useful innovations for firms involved in coopetition relationships. It is crucial for firms that their managers balance their ambidextrous activities of exploration and exploitation so as to develop innovation ambidexterity.