Today, the sustainability supply chain is one of the hottest discussions in the world among practitioners, academicians, and governments. Therefore, Indonesia is a developing country that also pays more attention to involvement. Indonesia has the most significant coconut production in the world, followed by India and the Philippines. However, based on previous research, the sustainability of the coconut in Indonesia is under threat to supply chain operation. Therefore, it is necessary to determine the crucial indicators of sustainable practices to measure the performance of a sustainable supply chain system. This study aims to assess an instrument's content validity and inter-rater reliability to determine a set of crucial key performance indicators (KPIs) for the sustainable supply chain coconut industry. Initially, this study reviewed the existing sustainable supply chain indicators and developed a list of indicators suitable for the coconut supply chain. Then, the indicators were assessed and validated by a group of five experts. The validity test was analyzed using Aiken's V indexes and interclass correlation coefficient (ICC). The validity test showed that the percentage of Aiken V, 60.78% (31 indicators) were valid, and 39.22% (22 hands) were invalid. In the inter-correlation coefficients test using a 95% confidence level, the ICC value obtained for the economic dimension is .743, categorized as moderate reliability; the environmental dimension is .684 (moderate); and the social dimension is .845, categorized as good reliability, and the average measure of the ICC value was .76 (good reliability). In conclusion, Aiken’s V index was used to determine the number of indicators. Only 31 could be further used as an instrument to determine the critical indicators for coconut supply chain sustainability in Riau Province-Indonesia.