Retail stores that sell used products to secondary users have helped tremendously to improve environmental sustainability. The used products that are donated to these stores are cleaned and sold for reuse in another cycle, thereby preventing the products from going into landfills at the first post-consumer use phase. To enhance sustainability, multiple processes at the retail stores could be evaluated so that improvement strategies could be concentrated on the vital processes. This study shows that the Materiality Assessment could be applied to identify the processes that are most important to the stakeholders of the business. The results provide a guide to the management to direct its sustainability improvement efforts appropriately.