Purpose: That knowledge acquisition from external sources can play a pivotal role in product design is a well-known fact. However, knowledge acquisition need not play a pivotal role in every context; it is also documented to have a dark side (i.e. negative impacts). Specifically, given that product stewardship, by definition, calls on each party in the product life cycle – including suppliers – to share responsibility for the environmental impact of products, the purpose of this study is to answer the question “whether knowledge acquired from suppliers plays a beneficial role in the context of product stewardship?” Design/methodology/approach: This study focuses on the effect of knowledge acquisition on product stewardship and its subsequent effect on environmental performance. Given that the effect of knowledge acquisition could be moderated by firm-specific and relational factors, this study also considers the moderating role of knowledge exploitation and supplier opportunism. Using primary data, the hypotheses are tested using two-stage hierarchical ordinary least squares regression models involving valid instruments. Findings: Though extant research doubts that knowledge acquisition will always be beneficial, this study adheres to the tenets of knowledge-based view and hypothesize that knowledge acquisition is pivotal to product stewardship and its subsequent impact on environmental performance. But the results suggest an intriguing double-edged effect of knowledge acquisition; while its direct effect on product stewardship is nonsignificant, it seemed to have a significant positive moderating effect on the relationship between product stewardship and environmental performance. But whenever knowledge exploitation and supplier opportunism are maintained at ideal levels, this double-edged effect of knowledge acquisition is successfully negated. Originality/value: While knowledge acquisition is key for new product design, its specific role in the product design that incorporates environmental considerations is still not clear. By proposing that knowledge acquisition could instead have a double-edged effect within the unique context of product stewardship, the study makes an invaluable contribution to the extant literature on knowledge management within supply chain relationships.