Objective: This study aimed to analyze parents’ perceptions regarding adolescents’ screen use, signs of screen dependency, and its impact on sleep among 10- to 16-year-olds in the district of Leiria, Portugal. A descriptive–correlational, cross–sectional study was conducted in April 2024 using an online questionnaire completed by a non-probabilistic accidental sample of 616 parents or legal guardians. Nearly half of the respondents (48.2%) perceived adolescents as dependent on screens, while 68.7% believed that their screen time was excessive. Several behavioural signs consistent with digital dependence were reported. Increased screen use was significantly associated with shorter sleep duration, daytime sleepiness, and difficulties initiating sleep. Although many adolescents still achieved the recommended number of hours of sleep, those perceived as screen-dependent were more likely to experience compromised sleep quality and quantity. These findings reinforce the growing concern about adolescents’ digital habits and underscore the importance of implementing targeted health promotion strategies focused on responsible screen use and sleep hygiene among school-aged youth.