Although most individuals consider gambling to be an innocent and fun activity, when it develops into problem gambling, it can have detrimental outcomes to one's life, such as over-indebtedness. This cross-sectional study explores the role of maladaptive personality traits and gender in both problem gambling and over-indebtedness, in an online sample of 1479 adult gamblers (65% males) in Sweden. Participants were administered the Problem Gambling Severity Index (PGSI), the Personality Inventory for DSM-5-Brief Form (PID-5-BF), and questions addressing subjective over-indebtedness and other risk factors. Quasi-Poisson loglinear models and logistic regression analyses demonstrated that Disinhibition ( = 1.38, 95% CI [1.24, 1.53]), and Antagonism ( = 1.23, 95% CI [1.14, 1.34]) showed the strongest associations to problem gambling, and that only Disinhibition ( = 1.72, 95% CI [1.22, 1.43]) and Antagonism ( = 2.00, 95% CI [1.52, 2.66]) were significantly related to over-indebtedness. The prevalence of problem gambling and over-indebtedness was more common among women, and gender moderated the univariate relationships of Negative Affectivity, Disinhibition and Psychoticism to problem gambling. These findings call for future research addressing maladaptive personality traits, problem gambling and over-indebtedness, and highlight the need for tailored interventions and prevention strategies, particularly for women who may be at higher risk.