The aim of this study was to translate and adapt the physical activity and leisure motivation scale (PALMS) into Spanish, and to analyse its validity and reliability. The sample comprised 867 adolescents, with a mean age of 14.04 ± 1.19 years, 53.9% of whom were male. During the translation process, some of the items in the instrument were modified slightly, improving its comprehensibility. On the other hand, the exploratory factor analysis did not present an adequate factor structure, so a more in-depth analysis was carried out, using item response theory and confirmatory factor analysis; the conclusion was that it would be appropriate to eliminate several items from the scale. From this, a final shortened version, consisting of 25 items, was produced, with adequate fit indices—CFI = 0.933, TLI = 0.918, SRMR = 0.042, RMSEA = 0.052 (90% CI 0.048; 0.056)—and good reliability for each of the dimensions, ranging from 0.625 to 0.835. It can be concluded that the abbreviated version of the PALMS instrument, adapted for Spanish adolescents (PALMS-e), is a valid and reliable instrument for assessing their motives for doing physical activity.