Questionnaires are frequently used for measuring physical activity. The aim of this study was to validate the Spanish version of the Minnesota Leisure Time Physical Activity Questionnaire (MLTPAQ) in Spanish men. Healthy men (n = 187) aged 20-60 years were recruited. The MLTPAQ was administered to assess the quantity (total activity metabolic index) and quality (heavy, moderate, and light) of physical activity performed in the last year, quarter, month, and week. Fitness was assessed with an exercise test. Spearman's correlation coefficients between the total activity metabolic index and exercise test duration, time to maximal theoretical heart rate, and caloric intake were 0.57, 0.46, and 0.40, respectively. The intraclass correlation coefficients between the total activity metabolic indexes in the last year and in the last quarter, month, and week were 0.62, 0.46, and 0.35, respectively. In multiple linear regression, the heavy, moderate, and light activity metabolic index, age, body mass index, and basal heart rate explained 40% of the variability of time to the maximum theoretical heart rate. The Spanish version of the MLTPAQ is a valid instrument to measure the quantity and quality of physical activity performed in the last year (also in periods shorter than 1 year) by Spanish men aged 20-60 years. Only heavy physical activity is related to cardiorespiratory fitness.