Although there is abundant evidence supporting an active lifestyle, it is necessary to promote the practice of physical activity among the population. To understand this phenomenon, several studies have been conducted to describe the reasons why people participate in sports activities. The PALMS (Physical Activity and Leisure Motivation Scale) was created as a comprehensive tool to measure the reasons for practicing sports. This tool consists of 40 items related to sports and is designed for the young and adult population. Each of the subscales is formed of five items (mastery, enjoyment, psychological condition, physical condition, appearance, the expectations of others, affiliation, competition/ego) that reflect the possible reasons for practicing sports. This study sought to validate the PALMS in the cultural context of Spain, for the type of population for which it is designed. In total, 596 voluntary participants completed the study from Spain, aged 18 to 53, who regularly practice sports. The adequacy of the model obtained in the exploratory study was confirmed, since a model composed of eight factors and 40 indicators in total was obtained. The parameters were statistically significant (p < 0.05) and the factor loadings presented values greater than 0.5. Regarding internal consistency, the values of Cronbach’s alpha and those of the composite reliability were above 0.8. In conclusion, the validation of the Spanish PALMS proved to be a valid and reliable measurement instrument for the evaluation of the reasons that lead the population to perform sports physical activity.