Brands’ self-operated live streaming commerce is a novel marketing approach, yet the mechanisms underlying consumer brand engagement remain unclear. This study draws on Uses and Gratifications theory and employs partial least squares structural equation modeling (PLS-SEM) together with necessary condition analysis (NCA) to examine the antecedents and outcomes of consumer brand engagement within the context of the apparel industry. Using purposive sampling, data were collected from 332 Chinese apparel brands’ self-operated live streaming commerce consumers. The results further demonstrate that perceived information usefulness, perceived enjoyment, economic benefits, and social support are significant and necessary motivations of consumer brand engagement. Moreover, consumer brand engagement serves as a significant and necessary condition for brand trust and brand loyalty, while it is not a necessary condition for self-brand congruity. This research assists marketers in optimizing brand self-operated live streaming commerce.