Digital projects aspiring to reach target audiences are executed through decentralized and trustworthy blockchain platforms (BPs). Once the objectives and target audience of a digital project are defined, the selection of suitable BPs is undertaken. The primary objective of this research is to develop a decision support system that aids in the selection of BPs for transferring digital data and assets. Numerous quantitative parameters determine the performance of BPs, alongside qualitative parameters indicating their performance. In this study, the aim is to determine the performance of BPs based on both qualitative and quantitative parameters. Within this scope, a multi-criteria decision-making approach and interval-valued spherical fuzzy (IVSF) sets are adopted. IVSF sets are utilized to determine expert importance levels. The IVSF-criteria importance assessment (CIMAS) method is introduced for the weighting of criteria. IVSF-CIMAS enables the determination of reliability levels in calculating criterion weights. The IVSF-simple weighted sum product (WISP) method is formulated to obtain the performance ranking of BPs. Thus, in this research, the IVSF-CIMAS-WISP hybrid model is developed, and an algorithm for this novel decision-analytic model is presented. A case study is developed focusing on BP selection for a digital project to demonstrate the applicability of the proposed hybrid model. The robustness of IVSF-CIMAS-WISP is tested through extensive sensitivity analysis scenarios. According to the research results, the applicability of the IVSF-CIMAS-WISP hybrid method is supported and its robustness is confirmed. The research findings provide numerous insights for project managers and practitioners. •The interval-valued spherical fuzzy CIMAS-WISP hybrid model is formulated.•The blockchain platform selection problem for digital projects is addressed.•The presented IVSF-based group decision-analytic tool is generalizable and robust.•A novel MCGDM-based perspective on the selection of blockchain platforms is offered.•Analytical insights and implications for project managers and practitioners are given.