Grounded in team production and agency theory, we investigate investment bank opportunism in the context of 466 foreign initial public offerings (IPOs) in U.S. equity markets from 2009 to 2023. Findings reveal that IPO underpricing is higher for foreign firms underwritten by larger and more diverse syndicates owing to concerns about free-riding and moral hazard. Our results are robust to a series of sensitivity tests. Moreover, frequent foreign IPOs by home-country firms and strong home-country legal protection for investors attenuate the positive relationship between underwriting syndicate size and diversity and IPO underpricing. By delineating the collaborative nature of IPO underwriting, this study offers new insights into the implications of syndicate structure for foreign IPO performance.