Nutritional warnings have gained popularity, particularly in the region of the Americas, to facilitate the identification of products with excessive content of nutrients associated with non-communicable diseases and encourage healthier food choices. Although warnings have been shown to be effective, an in-depth understanding of the reasons why some consumers do not use them is still lacking. The aim of the present work was to explore self-reported use of nutritional warnings and to identify the reasons for not considering nutritional warnings for making food purchase decisions after policy implementation in Uruguay. A non-probabilistic sample of 858 Uruguayan participants was recruited using an advertisement on Facebook and Instagram. Through an online survey, self-reported use of nutritional warnings was asked using a closed-open ended questions. Participants who reported not considering warnings to make their purchase decisions were asked to explain the reasons why using an open-ended question. Responses were analysed using deductive coding, based on the Behavioural Drivers Model. Thirty seven percent of the participants stated that the warnings had not influenced their purchase decisions. Motives for not being influenced by the warnings were related to lack of interest, attitudes, lack of perceived self-efficacy, cognitive biases and limited rationality when making purchase decisions. In addition, structural barriers, such as availability, cost and trust in the food industry also emerged from participants’ responses. Strategies to encourage the use of warnings should include communication campaigns and policies to address structural barriers related to the perceived availability and affordability of healthy foods.