Plain cigarette packaging, which seeks to remove all brand imagery and standardize the shape and size of cigarette packs, represents a novel policy measure to reduce the appeal of cigarettes. Plain packaging has been studied primarily in high-income countries like Australia and the UK. It is unknown whether the effects of plain packaging may differ in low-and-middle income countries with a shorter history of tobacco regulation, such as Mexico. An experimental study was conducted in Mexico City to examine perceptions of branded and plain cigarette packaging among smoking and non-smoking Mexican adolescents (n = 359). Respondents were randomly assigned to a branded or plain pack condition and rated 12 cigarette packages for appeal, taste, harm to health and smoker-image traits. As a behavioral measure of appeal, respondents were offered (although not given) four cigarette packs (either branded or plain) and asked to select one to keep. The findings indicated that branded packs were perceived to be more appealing (β = 3.40, p < 0.001) and to contain better tasting cigarettes (β = 3.53, p < 0.001), but were not perceived as less harmful than plain packs. Participants rated people who smoke the branded packs as having relatively more positive smoker-image traits overall (β = 2.10, p < 0.001), with particularly strong differences found among non-smokers for the traits ‘glamorous’, ‘stylish’, ‘popular’ and ‘sophisticated’ (p < 0.001). No statistically significant difference was found for the proportion of youth that accepted when offered branded compared with plain packs. These results suggest that plain packaging may reduce brand appeal among Mexican youth, consistent with findings in high-income countries.