In this study, we propose an index to measure the degree of customer involvement in the creation of innovative businesses. According to the Lean Startup approach, involving customers at early stages of new business creation increases the likelihood of success (Ries 2011; Blank & Dorf 2012), but is this really the case? It is difficulty to answer this question because we lack theoretically consistent measure of customer involvement during new venture creation. Our study intends to fill in this gap by proposing an index of customer involvement. It can be conceptualized by looking at the intensity and the content of exchanges between an emerging business and its customers (Gruner and Homburg, 2000; Roser et al., 2013). The notion of business model, on the other hand, describes the architecture of an innovative business (Amit and Zott, 2011; Chesbrough and Rosenbloom, 2002). We mix these two streams of literature to design a measurement tool of customer involvement. For the five customer-related blocks of business model (Osterwalder, 2004), we propose four dimensions of customer involvement: size of the interaction, frequency of interaction, level of contribution and the exploitation of customer feedback.