Background: The current study aims to identify predictors of pathological gambling (PG) severity, taking gender differences into account, in an outpatient sample of pathological gamblers seeking treatment. Methods: The sample for this study consisted of 103 subjects (51 women and 52 men) meeting current DSM-IV-TR criteria for PG. Linear and logistic regression analyses were used to examine different risk factors (gender, age, impulsivity, sensation seeking, self-esteem) and risk markers (depression, anxiety, gambling-related thoughts, substance abuse) as predictors of PG severity. Results: Impulsivity, maladjustment in everyday life and age at gambling onset were the best predictors in the overall sample. When gender differences were taken into account, duration of gambling disorder in women and depression and impulsivity in men predicted PG severity. In turn, a high degree of severity in the South Oaks Gambling Screen score was related to older age and more familiy support in women and to low self-esteem and alcohol abuse in men. Female gamblers were older than male gamblers and started gambling later in life, but became dependent on gambling more quickly than men. Conclusions: Further research should examine these data to tailor treatment to specific patients’ needs according to sex and individual characteristics.