Background: Front-of-Pack Nutrition Labelling (FOPNL) is a promising public health measure to promote healthier food choices and so curb weight gain in the population. The most frequently used labels are the Nutri-Score (in Europe) and warning labels (in the Americas). The present study aimed to test acceptability of the two labels and their impact on purchasing intentions and product perceptions in Indonesia and Turkey, where no FOPNL system is currently in place, and Mexico, where warning labels are mandatory since October 2020. Methods: Adult participants from Indonesia, Mexico and Turkey (N = 639; nIndonesia = 212, nMexico = 203, nTurkey = 224) indicated use of nutrition information on food packaging and acceptability of the two FOPNL systems. They were then randomly assigned to viewing eight product pairs (chips, instant noodles, meats, condiments, sweet spreads, cookies, yoghurt, fruit drinks) with either no label, a Nutri-Score, or warning labels. They indicated which product (or neither) they would rather buy, and which product was healthier, contained more calories, sugar, saturated fat, and sodium.Results: Acceptability of labels was high, with small country differences (partial η²s ≤ .04). Nutri-Score influenced purchasing intentions for four categories (ORs 2.38 – 4.55); warning labels only for one (OR = 2.45). Overall, Nutri-Score was somewhat more effective in guiding consumers to identify healthier choices (ORs 2.43 – 12.78) and products higher in nutrients that should be consumed in moderation (ORs 0.45 – 9.62) compared to the warning labels (healthiness: ORs = 0.52 – 6.70; nutrients: ORs = 0.44 – 20.66), although effects varied substantially between product categories and nutrients.Conclusions: Both Nutri-Score and warning labels are mostly accepted and potentially promote healthier food choices, with Nutri-Score producing somewhat larger and more consistent effects. Interestingly, significant effects for the Nutri-Score were sometimes driven by a shift from participants choosing to buy neither product to buying the product with the better Nutri-Score, indicating potential health halo or self-licensing effects. Thus, more research is needed on potential negative consequences on food choices and the conditions under which they might appear to maximize public health impact.Trial registration: https://osf.io/45msn