The aim of this study was to evaluate the association between food consumption by the degree of processing and sleep quality in adolescents from São Luís, Maranhão, Brazil. A cross-sectional study with 2499 adolescents (aged 18 to 19 years) was developed. Exposure variables included energy contributions of food groups stratified by the NOVA classification: fresh or minimally processed foods (FMPF), processed foods (PF), and ultra-processed foods (UPF), categorized into quartiles. The outcome variable was sleep quality assessed with the Pittsburgh Sleep Quality Index. Associations between these variables were estimated by Poisson regression, with robust estimation of variance. Most of the adolescents had poor sleep quality (57.1%). There were associations between FMPF in the third (57.1%–66.0% of total calories; prevalence ratio PR = 0.88; 95% CI: 0.80, 0.97) and fourth quartile (66.1%–95.8% of total calories; PR = 0.87; 95% CI: 0.78, 0.96) and lower prevalence of poor sleep quality. The fourth quartile of UPF (44.3%–81.8% of total calories; PR = 1.14; 95% CI: 1.03, 1.27) was associated with a higher prevalence of poor sleep quality. Higher intake of FMPF is a protective factor for poor sleep quality, whereas higher UPF consumption is a risk factor for poor sleep quality.