PurposeWaterpipe tobacco smoking (WTS) has substantially increased among young people in Lebanon, who perceive WTS as safer than cigarettes. Health warning labels (HWLs) can inform the adverse effects associated with smoking. Thus, their application to waterpipe offers a favourable policy to limit WTS epidemic. This study assessed the effectiveness of pictorial HWLs and their placements on waterpipe parts (device, tobacco and charcoal package) on several communication outcomes.MethodsWe conducted a randomised cross-over experimental study among 276 waterpipe smokers (aged 18–34) between 13 and 26 August 2021. Participants observed three conditions: pictorial HWLs on tobacco packages, pictorial HWLs on three parts of the waterpipe (device, tobacco and charcoal package) and text only on tobacco package in random order. Participants completed baseline and postexposure assessments evaluating HWL effectiveness on attention, reaction, attitudes and beliefs, perceived effectiveness of HWLs and intention to quit WTS. Planned comparisons using Friedman test followed by pairwise Wilcoxon signed-rank test for multiple comparisons were conducted.ResultsCompared with text only, pictorial HWLs elicited greater attention (p=0.011), higher cognitive elaboration (p=0.021), perceived message effectiveness (p=0.007), negative affect reactions (p<0.01) and greater psychological reactance (p=0.01). No significant differences were found for most communication outcomes between pictorial HWLs on three parts of the waterpipe compared with tobacco package only.ConclusionsPictorial HWLs on tobacco package were superior to text only for several communication outcomes. These findings provide strong evidence for potential implementation of pictorial HWLs on waterpipe tobacco packages to increase smokers’ awareness of the health effects of WTS and correct false safety perceptions.