This study aimed to (i) compare the food safety knowledge, attitudes, and self-reported practices (KAP) and observed food safety practices of food truck (FT) food handlers, (ii) evaluate the microbiological quality of food and water samples collected from these vehicles, and (iii) establish a score classification for the KAP instrument according to the food contamination probability assessment. This study was conducted in three stages with 40 food truck food handlers conveniently sampled in the Federal District, Brazil, through structured interviews, application of an observational checklist for the assessment of handlers’ practices and the collection of food and water samples for determination of microbiological quality. FTs that are likely to exhibit food contamination and are at a high risk of foodborne diseases if at least one of the following situations occur: (1) if a food handler scores ≤6 in the knowledge section; (2) if a food handler scores ≤5 in the attitudes section; or (3) if a food handler scores ≤6 in the self-reported practices section. On the other hand, FTs in which handlers score higher than the cutoff points in all the sections are unlikely to exhibit food contamination and are at a low risk of foodborne diseases. The findings of this study are the first step to understand food handlers’ point of view and the initial diagnosis to guide educational strategies in the FT sector.