Influencers who promote health-related products on digital platforms can cause physical and financial harm that ordinary consumers can rarely trace back to a single actor. This article examines the civil liability of influencers for such harm under Vietnamese law after the 2025–2026 reforms, namely Law No. 75/2025/QH15 amending the Law on Advertising, the Law on E-Commerce No. 122/2025/QH15 and Decree No. 248/2026/ND-CP, read together with the 2015 Civil Code. Using doctrinal and comparative methods, it compares Vietnam with China, which ties joint liability to the nature of the product and the endorser’s knowledge, and with Australia, whose regulator-led model targets both influencers and the brands that instruct them. The article identifies four gaps: an undefined fault standard for influencers, no differentiation between ordinary products and those affecting life and health, weak evidentiary access for victims, and limited tools for dealing with repeat endorsers. It proposes five de lege ferenda measures: a risk-based verification standard, a rebuttable presumption of fault for health-related endorsements, mandatory record-keeping by platforms, seller–influencer risk-allocation clauses, and graduated bans from endorsing sensitive products.