Hypersexuality is a problematic behavior characterized by the combination of an excessive sexual desire and the pathological inability to control it. This study presents the psychometric properties of the Spanish paper-and-pencil and online versions of the Hypersexual Behavior Inventory (HBI), one of the most popular scales to assess this issue. A total of 2,250 participants (1,070 men) completed a translated version of the HBI (1,450 in paper-and-pencil; 800 online). The exploratory factor analysis yielded three factors that explained 67.53% of total variance for the HBI paper-and-pencil version. This factor structure was confirmed in the HBI online version through confirmatory factor analysis (CFA). Factorial, structural, scalar and error variance-invariance according to gender was also confirmed through multigroup CFA. Reliability of the total score and subscales ranged between .89 and .96. Likewise, correlations with other related scales were positive and significant (r between .511 and .743). Temporal stability one year after the first application was .77 (paper-and-pencil format) and .68 (online version). These results support the reliability and validity of the HBI and justify its use in the assessment of hypersexuality in Spanish-speaking countries.