PurposeClose relationship with major customers, by curtailing opportunistic behaviors during private placements (PPs) and guaranteeing the production and sales of products after, is expected to facilitate the realization of PP’s strategic goals. However, major customers, on the contrary, may impair PP’s performance because of their strong bargaining power. Based on the transaction cost theory and relational contract theory, this paper aims to investigate the impact of major customers on firms’ strategic development in the context of private placements. The mechanisms of such impact are analyzed from the prospect of economies of scale, supervision and the rip-off effect by major customers. Further, the moderating role of the customer relationship investment (CRI) is considered.Design/methodology/approachUsing a sample of China’s non-financial A-share listed firms during 2010-2016, this paper empirically investigates the impact of customer relationships on firms’ operating performance following PPs. In the main regressions, the sales growth rate serves as the dependent variable to measure PP’s operating performance, while the customer concentration proxies for the closeness of customer relationship. This study captures the impact of customer relationships on PPs’ performance by looking at the coefficient of the interaction term of post PP dummy and customer concentration. In the additional tests, selling and management expenses along with entertainment and traveling expenditures are used to measure customer relationship investment.FindingsResults show that major customers help improve PPs’ strategic performance. The more concentrated the customer portfolio is, the higher operating performance will be after the PPs. Such a relationship is stronger when CRI is at a higher level. However, CRI also incurs costs, which impairs the effect of major customers on net profit. Further research finds that the effect of major customers is more pronounced in situations of extensional PPs, with actively interactive customers and in non-state-owned firms. In addition, state-owned customers with strong bargaining power have impaired the role of customers in promoting PP’s operating performance.Originality/valueThis paper validates the role of customers in firms’ strategic development. The study not only contributes to the research on the economic consequences of customers but also adds to the evolving literature of factors affecting the performance of PPs. The findings of the study have important practical implications for both customer relationship management and the supervision of PPs.