Purpose This paper aims to report the development of the multiparty collaborative leadership scale (MCLS) that assesses four dimensions of collaborative leadership that have been defined in the literature regarding the functions of collaborative leadership in intra- and interorganizational settings. Design/methodology/approach The authors have tested the validity and reliability of the MCLS in a sample of 110 managers and professionals who participated in five multiparty collaboration workshops, each lasting for two days. The authors used multilevel analyses to test the construct, discriminant and predictive validity of the MCLS. Findings The results generally supported the reliability and validity of the MCLS. The scale has good internal consistency and in terms of validation, the authors show that MCLS negatively predicts the conflictuality and positively predicts the collaborativeness of the leading party as well as trust in the multiparty system and its entitativity. Research limitations/implications The MCLS can be used to extend literature on collaborative leadership and generate insights on the antecedents and consequences of effective collaborative leadership in multiparty systems. Social implications Multiparty systems are set to deal with important societal challenges and mediators involved in multiparty issues are asked to settle important international disputes and conflicts. Understanding collaborative leadership in such systems and its role in establishing effective multiparty collaboration is key. The MCLS can be used as a research instrument and as a development tool toward realizing much-needed collaboration. Originality/value The authors present a first attempt to develop a short scale to assess collaborative leadership in complex systems in which participating stakeholders lack position power.