Portfolio innovativeness is a central variable in innovation management. However, the impact of portfolio innovativeness on new product development (NPD) performance is unclear, which may partly be due to the construct's multifaceted nature. Different facets may reflect different degrees of innovativeness and may have different relationships with performance. In addition, firm members with different functional backgrounds may perceive and thus assess these facets differently, which again may influence the performance effect of portfolio innovativeness. Based on a sample of 746 CEOs and marketing as well as technology professionals from 117 firms and using Item Response Theory (IRT), a multifaceted scale of portfolio innovativeness, whose facets are able to cover the entire innovativeness spectrum, is developed. In addition, it is shown that the performance impact of portfolio innovativeness is dependent on the facets included in the scale, and on the specialization of the professional assessing the facets. Inverted U-shaped performance effects are found when the scale covers the entire spectrum of innovativeness, and linear positive or zero effects with different types of more narrowly modeled scales. Inverted U-shaped performance effects are also found when technology professionals assess the facets, while the assessments by marketing professionals lead to linear positive effects.