The US Spanish-speaking population has rapidly increased in recent years and there is a need for valid Spanish measures to assess gambling behaviour. This study reports on the development of a Spanish measure of self-efficacy to control gambling behaviour (Gambling Self-Efficacy Questionnaire [GSEQ]; May, Whelan, Steenbergh, & Meyers, 2003). One hundred and eighty-seven Spanish-speaking individuals residing in the south-east United States completed the 16-item measure. The GSEQ-Spanish version (GSEQ-S) showed high internal consistency (α = 0.99) and evidence of convergent and discriminant validity. Factor analytic data supported a single factor structure similar to that found with the English version. As expected, pathological gamblers scored significantly lower on the GSEQ-S than non-pathological gamblers. The results provide initial psychometric support for the GSEQ-S and suggest that the measure can be used as a valid assessment of gambling self-efficacy among Spanish-speaking gamblers. Further evaluation of the psychometric properties of this instrument is suggested.