Abstract Introduction Pictorial health warning labels (HWLs) on waterpipe (WP) tobacco packages represent a better strategy for communicating the health risks associated with WP use and promoting quit intention than text-only. However, the mechanism by which these warnings lead to higher intentions to quit remains unknown. Aims and Methods This study explores how pictorial warnings versus text-only induces higher quit intention among a sample of young adult WP smokers in Lebanon. An online randomized cross-over experimental study was conducted in August 2021 among 276 young adult WP smokers who were exposed to two conditions: pictorial HWLs and text-only warnings on WP tobacco packages in random order. After each image, participants completed post-exposure assessments of health communication outcomes (eg, attention and negative affect). Using serial and parallel mediation analysis, we examined the role of attention, negative affect, cognitive elaboration, and perceived harm in mediating the relationship between exposure to HWLs and intention to quit. Results Using serial mediation, exposure to pictorial warnings versus text-only was found to affect intention to quit through the following pathways: attention and negative affect, which accounted for 17.28% of the total effect, and through negative affect and cognitive elaboration, which accounted for 21.53% of the total effect. Results of parallel mediation showed that the indirect effect pathways via negative affect (β = 0.063; [95% bootstrap CI = 0.004 to 0.149]) and cognitive elaboration (0.047; [0.001 to 0.114]) were statistically significant. Conclusions The findings call on designing and implementing attention-grabbing, emotionally evocative, and cognitively persuasive pictorial warnings in Lebanon and other countries to curb WP tobacco smoking. Implications This is among the first experimental studies looking at multiple mediators underlying the effect of exposure to pictorial HWLs on intention to quit in a sample of current WP smokers in Lebanon. The findings showed that using attention-grabbing, emotionally evocative, and persuasive pictures with a clear textual warning is crucial to maximizing the impact of implementing WP-HWLs regulations in Lebanon and other countries to curb WP tobacco smoking.