The current study examined the efficacy of health warnings on caffeinated energy drinks (CEDs). Participants aged 12-24 years (n = 2040) completed an online survey where they were asked to recall any existing warning statements on CED products and were randomized to one of 29 experimental warning conditions. Regression models were fitted to examine differences between conditions in product appeal, perceived safety and message recall. Overall, fewer than 30% of participants were able to accurately describe an existing CED product warning. Experimental findings indicated that exposure to CEDs with warning labels resulted in greater recall. Warnings on the back of CED cans featuring large font, a border, and a 'caution' heading resulted in significantly greater recall (P < 0.05 for all). Front-of-package 'High source of caffeine' labels resulted in greater recall than a quantitative description (P < 0.001); caffeine labels generally elicited lower product appeal (P < 0.001) and perceived safety (P = 0.002) ratings vs. no caffeine labels, and the qualitative caffeine statement elicited lower perceived safety ratings than the quantitative statement (P = 0.02). Existing warning statements in Canada have low levels of awareness. Warnings on CEDs could be enhanced to increase the salience of messages, with greater impact from clear, descriptive, front-of-package 'High source of caffeine' labels.