We present development and validation of the Digital Addiction Scale for Teenagers (DAST), describing the pilot study (N = 40 students) and main study (N = 4493) with Estonian students aged 11–19, in spring 2020. Our aim was to create a scale suitable for psychoeducational assessment of teenagers’ behaviour and feelings towards digital devices. We used the mixed research framework (Onwuegbuzie, Bustamante, & Nelson, 2010). Half of the study sample was collected before the coronavirus crisis (Sample 1: 1972 students) and the rest of it during a distance learning period (Sample 2: 2521 students). We found that factor structure in both subsamples were similar. The DAST shows a negative relation with emotional school engagement and life satisfaction and positive correlations with school burnout, learning difficulties and screen time. We discuss potential uses of the scale for assessing health related digital competences.