This study investigates smartphone addiction prevalence among Tunisian middle school students and its associations with sleep quality, fatigue, cognitive functioning, and academic achievement. Using structured interviews, we collected demographic data, grade point averages, and phone usage details from 1015 students aged 14-16. Participants also completed the smartphone addiction scale: short version (SAS-SV), fatigue assessment scale (FAS), Pittsburgh sleep quality index (PSQI), and cognitive failures questionnaire (CFQ). The results categorized 85.1% as "normal smartphone users" (NSUs) and 14.9% as "problematic smartphone users" (PSUs). Troublingly, higher SAS-SV scores correlated with poorer sleep quality, increased fatigue, and impaired cognitive functioning. Lower academic achievement was also associated with elevated SAS-SV scores. Though the percentage of addicted students seems modest, addressing smartphone addiction in Tunisian middle schools is crucial due to its associations with various psycho-physiological and cognitive impairments, underscoring the need for intervention strategies.