This article introduces and discusses the 15-item Scale for the Integrative Mindset (SIM) of negotiators, that is of people involved in joint decision-making processes. The scale is based on the integrative mindset (Ade, Schuster, Harinck, & Trötschel, 2018), which describes a set of three inclinations of parties approaching negotiations: a collaborative, a curious, and a creative one. Using a first sample (N = 1,030) of online survey participants, we provide evidence for a high psychometric quality of the SIM as suggested by high reliabilities and good fit indices. We also compare the SIM with scales that measure well-known and possibly related psychological constructs and show the SIM’s distinction to them. Using a second sample (N = 417), we show how the SIM differs from a Scale on Inappropriate Negotiation Strategies (SINS) that has been used in previous negotiation research. The findings of the present studies are discussed with respect to potential applications of the SIM in experimental research.