This study examined (a) differences in estimates of Problematic Mobile Phone Use (PMPU) in adults across 14 countries worldwide and (b) whether personality and psychopathology variables predict PMPU. A sample of 7531 adults (69.6% women; mean age 25.7, SD = 9.9) completed an online survey about PMPU, defense mechanisms, coping strategies, self-esteem, pathological personality traits, and depressive symptoms. The overall mean PMPU score was 104.3 (range 27–270) and 28.1% of the participants self-reported PMPU. Women had significantly higher PMPU overall. Consistent predictors of increased PMPU in the overall sample were younger age, female gender, more hours spent on mobile phone, coping strategies, immature and autistic defenses, depression, and six personality disorders. Significant differences across countries were found in means, self-reported rates, and predictors of PMPU (hours spent, dependent personality, depression, and immature defense were common). Findings pave the way for evidence-based prevention and policy efforts at the public health level.