The number of gadget users (smartphones) globally is increasing yearly. Gadgets are also used as learning media and entertainment for students, so the possibility of negative impacts from using gadgets cannot be avoided. This study aims to analyze the relationship between the intensity of gadget use and depression, anxiety, and stress in students. This cross-sectional study was conducted on 461 students recruited using a multistage random sampling technique, from six public high schools (SMAN) in Metro, Lampung, Indonesia, from February to May 2023. The instruments used were the gadget usage intensity questionnaire and the Depression Anxiety Stress Scale (DASS)—analysis with a Chi-Square correlation test. The results of the study show that there is a significant relationship between the intensity of gadget use and depression (ρ-value < 0.001), anxiety (ρ-value < 0.001), and stress (ρ-value < 0.001). This study concludes that the intensity of using gadgets is related to depression, anxiety and stress in high school students in Metro City, Lampung, Indonesia. It is recommended that schools carry out outreach and education to students to be wiser in using gadgets and to follow up on respondents who experience health problems with depression, anxiety, and stress by coordinating with parents so that they can receive further treatment at health care facilities.