Case evidence has shown the important role of individual level assimilation of ERP technology in realizing the business value of implemented ERP systems. However, empirical research in this area has been constrained by the lack of a validated scale for measuring individual level ERP assimilation. This study address this limitation by first theoretically conceptualizing three key dimensions through a multi-case study and then following a rigorous development process to validate a formative measurement instrument for individual level ERP assimilation. The findings show that individual level ERP assimilation consists of width, depth, and innovation, and the proposed measurement instrument is reliable and meets the validity requirements.