Innovation sourcing is the acquisition and integration, rather than internal development, of critical knowledge from external providers. This key strategy has emerged as a necessity for survival in many markets. Consequently, sourcing processes are applied to complement internal design capabilities with external knowledge and ultimately improve innovation performance. Firms use external knowledge to enhance products and services, gain market share, and improve profits. The literature regarding the phenomenon of innovation sourcing is largely fragmented, limiting the theoretical advancement in the field. This article presents a systematic literature review that synthesizes the body of knowledge regarding innovation sourcing and derives a conceptualization of how innovation sourcing and its main dimensions are linked to innovation performance. A conceptual model, key dimensions, and an agenda for future research are significant results of this research.