Business exchange and industrial marketing literature has long investigated determinants of long-term buyer-supplier relationships (BSRs). Anecdotes of BSR dissolutions may suggest that long-term relationships are potentially fragile as circumstances can shift and undermine such relationships, leading to buyers discarding their long-term suppliers. This study investigates supplier attributes that potentially enable suppliers to develop impregnable exchange relationships (IERs) with buyers. We use a multi-theoretical lens of strategic, relational, and behavioral perspectives to guide our research. Based on these perspectives, we maintain that economic necessity, relational ties, and emotional connections with their buyers are all important determinants of IERs. Using the repertory grid technique and post-hoc interviews with purchasing managers, we identify four supplier primacy attributes, helpfulness, friendliness, uniqueness, and flexibility. They co-occur and potentially aid suppliers in attaining economic necessity, relational ties, and emotional connections with buyers. Our findings also suggest that suppliers may alternatively advance toward the development of IERs with buyers through certain combinations of lower-level attributes to compensate for their lack of those four primacy attributes. Finally, we find that joint history between suppliers and buyers may bring about buyers negative perceptions on suppliers.