Over the years, scholars have sought to test concepts and theories in consumer research and marketing strategies that are produced from the perspective of both developed and emerging markets, in order to discover the differences between them. Some of these efforts have helped deepen our comparative understanding of the two types of markets. More often than not, however, they present a limited perspective, failing to make theoretical advances and offering few implications for companies in other geographical and economic contexts. Such attempts blur our understanding of the true nature of, for example, emerging markets and the significant ways in which their market structures differ from those of developed markets. The authors of marketing and management concepts and theories are influenced by their environments, which are mostly developed markets. Mere replication of these markets, without proper contextual delineation, offers little that relates to the important contributions being made by emerging markets to the world’s economy (Sheth, 2011). The contribution this article makes is in empirically testing the relationship between the customer involvement capabilities of service firms and firm performance in these two different types of markets. This comparative perspective both expands the theoretical boundaries of the discipline of marketing and provides significant practical benefits and managerial implications for service firms and practitioners in both developed and emerging markets. This study argues that, given specific market constraints, the effect of customer involvement capability may not always be positive and that some boundary conditions may therefore better explain how involvement capability improves firm performance. This study investigates the direct effect of customer involvement capability on firm performance and the possible mediating role of innovation in two countries, the United Kingdom and Ghana. According to Maheswaran and Shavitt (2000) and Bagozzi (1994), cross-country research such as this can help to validate theoretical paradigms, enrich current theorization, and may even lead to new theories. The study enriches the theorization of the effect of involvement capability by explaining some boundary conditions which improve firm performance in different markets. The general customer/market orientation literature gives credence to the importance of customers in creating value for both the customer and the firm (see Appiah-Adu & Singh, 1998; Han, Kim, & Srivastava, 1998). There is an increasing role for customers in the production and delivery of service (Jaakkola & Alexander, 2014). Indeed, Carbonell, Rodríguez-Escudero, and Pujari (2009) argue that customer involvement in new service development greatly impact a firm’s fortunes. The customer participation and involvement literature shows that service firms are actively involving their customers in the production and delivery of service to co-create value (Gallan, Jarvis, Brown, & Bitner, 2013; Grönroos, 2008). In the concept of the joint sphere of the cocreation of value posited by Grönroos and Voima (2013), the customer has a double role: “co-producer of resources and processes with the firm; and value creator jointly with the firm” (p. 140). Customers are now being viewed as proactive co-creators, rather than as passive receivers of value (Chan, Yim, & Lam, 2010; Vargo & Lusch, 2004).