Maladaptive daydreaming describes excessive fantasy activity that interferes with an individual's life. Surprisingly, the precursors of maladaptive daydreaming and its role in excessive involvement in virtual worlds have been scarcely investigated. In the current study, we examined the relationships among attachment styles, maladaptive daydreaming, and problematic social media use (PSMU) in a sample of community-dwelling adults. Eight hundred seventy-seven participants between 18 and 68 years old were recruited via an online survey and asked to fill out self-reported measures on attachment styles, maladaptive daydreaming, and PSMU. Mediation analyses showed that maladaptive daydreaming is a significant mediator in the relationships between preoccupied and fearful attachment styles and PSMU, suggesting that maladaptive daydreaming partly explains the established link between insecure attachment styles and excessive use of social media. Individuals with PSMU fostered by maladaptive daydreaming may benefit from clinical interventions that promote the use of adaptive regulatory strategies to develop feelings of security and self-confidence that may serve to reduce the excessive involvement in social media