The food industry and its supply chains have significant sustainability implications. Effective supply chain management requires careful consideration of multiple tiers of partners, especially with respect to sustainability issues. Firms increasingly approach their sub-suppliers to drive compliance with social and environmental efforts. A number of complexities and unique challenges make sub-supplier management more difficult than direct supplier management, e.g. a lack of contractual relationships to sub-suppliers, few opportunities to put direct pressure on sub-suppliers, or lack of transparency concerning sub-suppliers' involvement in a focal firm's supply chains. The literature has not investigated, either from sustainability or other perspectives, the critical success factors (CSFs) for firms' sub-supplier management. Therefore, this study seeks to explore and increase understanding of critical factors that help to overcome the complexities and unique challenges of sub-supplier management, with a focus on the food industry. Using data and information from a year-long field study in two food supply chains, the research identified 14 CSFs that influence the success of sub-suppliers' compliance with corporate sustainability standards (CSS). The identified CSFs can be classified into (1) focal firm-related, (2) relationship-related, (3) supply chain partner-related, and (4) context-related CSFs. The present research expands on the theory of critical success factors by applying the theory to the sustainability and sub-supplier management context. In support of critical success theory, it was found that CSFs do exist and their management will be necessary for effective sub-supplier management success as highlighted and exemplified by field study insights from practitioners. Multiple research avenues are necessary for further evaluation of sub-supplier management in the food industry and other industries who may find similar issues that arose from the food industry. •Critical success factors (CSFs) for sub-supplier management in sustainable food supply chain management are examined.•Fourteen CSFs influencing sub-suppliers' compliance with corporate sustainability standards are identified.•CSFs can be classified into (1) focal firm-related, (2) relationship-related, (3) supply chain partner-related, and (4) context-related CSF.•A one year field study was used to complete this research.•The theory of critical success factors is expanded to sustainability and sub-supplier management.