The diffusion of the internet and technological progress have made gambling on online platforms possible, also making it more anonymous, convenient, and available, increasing the risk of pathological outcomes for vulnerable individuals. Given this context, the present study explores the role of some protective and risk factors for problematic gambling in online gamblers by focusing on the interaction between alexithymia, dissociation, and family functioning. A sample of 193 online gamblers (Mage = 28.8 years, SD = 10.59; 17% females, 83% males) completed the South Oaks Gambling Screen, Twenty-Items Toronto Alexithymia Scale, Dissociative Experience Scale-II, and Family Adaptability and Cohesion Evaluation Scales-IV through an online survey. MANOVA, ANOVA and moderated mediation analyses were carried out to analyse the data. Significant differences in cohesive family functioning, alexithymia and dissociation have been found between online gamblers with problematic, at-risk or absent levels of gambling disease. Furthermore, the results showed a significant and positive association between alexithymia and problematic online gambling, partially mediated by dissociation, with the moderation of cohesive family functioning. Such data may have relevant clinical implications, highlighting the interaction of some core personal and environmental variables that may be involved in the etiology of online pathological gambling and could be kept in mind to tailor preventive interventions.