This multi-case study explores the digital sourcing practices of two complementor firms within two digital platform ecosystems (DPE) owned by Microsoft and SAP, respectively. We draw on organizational ambidexterity and social mechanisms as lenses to analyze how the two complementors address the paradoxical practices of exploration and exploitation within the context of their respective DPE. Our analysis suggests that the identified social mechanisms illustrate how each complementor engages in digital sourcing to create new ideas with other DPE actors that will nurture capability development (exploration) and transform these ideas into practice (exploitation). We identify two modes of ambidexterity, whereby one capability is used to improve the other, i.e., ‘exploration-for-exploitation,’ an orientation towards continually improving the quality of the service delivery, and ‘exploration-through-exploitation,’ an approach of project-driven learning.