As digital connectivity has become an integral part of daily life, internet addiction has emerged as a significant concern, particularly among adolescents. Therefore, this study aims to estimate the prevalence of internet addiction among adolescents, assess its severity, investigate the associations between sociodemographic factors and internet addiction levels, and examine the correlation between adolescents' age and the severity of internet addiction. This descriptive cross-sectional study involved 200 adolescents from private education institutes in Sargodha, Pakistan. A structured questionnaire was developed to collect data on sociodemographic indicators, and the validated Internet Addiction Test (IAT) questionnaire was adopted to assess the occurrence and severity of internet addiction. The data were analyzed using IBM® SPSS® software. The results revealed that among the 200 participants, 42% were male and 58% female, with nearly half (47.5%) being aged 13–15 years. Most (57.00%) owned a personal mobile device, whereas 47.5% had a laptop. Furthermore, 39.5% of the participants used the internet for one hour or less per day, whereas 30% reported using it for 2–4 hours daily. Only 8 participants stated that they did not use any social media applications. The study highlights significant internet addiction patterns. Many participants stayed online longer than intended (12.5% always, 16.5% often), whereas 34.5% neglected household chores. Internet dependency was evident, with 14.5% preferring online excitement over intimacy and 26.0% receiving complaints about excessive internet use. Sleep disturbances affected 25.0% of the study participants, whereas academic impacts were reported by 14.5% of the participants. The IAT results revealed that 8.5% of the participants had full control, 54.0% had mild, 36.0% had moderate, and 1.5% had severe addiction. Chi-square analysis revealed no significant associations between addiction severity and sex, age, or device ownership (p > 0.05), but the duration of internet use per day was significantly associated with addiction severity (p = 0.030). Age was weakly but significantly correlated with internet addiction (p = 0.04). The study concluded that a significant proportion of adolescents experienced moderate to severe internet addiction. These findings highlight the urgent need to implement measures to promote healthy digital practices among adolescents.