question: This proof-of-concept study aims to evaluate the effect of placing graphic health warning labels (GHWLs) on the ENDS device on users' experience, puffing patterns, harm perception, nicotine exposure, and intention to quit or use in the future. JUUL users (n = 26, age 18-24 years; 69% male; 85% Hispanic) were recruited to complete two 60 minutes ad libitum sessions that differed by GHWL on the device (GHWL vs. no-GHWL control) in an experimental clinical lab study. Compared to the control session, using JUUL with GHWL on the device was significantly associated with reduced positive experiences such as pleasure, product liking, and user satisfaction (p-value < 0.05 for all). Also, after exposure to GHWL, participants were less interested in using the same product again (p-value = 0.007), even if it was the only product available on the market compared to control (p-value = 0.03). Trends toward reduced puffing behavior and nicotine boost were also noted during the GHWL, compared to control sessions. This pilot study shows that placing GHWL on the ENDS device may be an effective and promising strategy to reduce ENDS use among young people.