Introduction: According to Self-Determination Theory, it is known that motivation is an essential factor for the adherence and enjoyment of exercise, generating long-lasting habits. The importance of generating such habits from an early age is a determining factor in the future health of people. The child and youth population invests a great amount of hours per week in their training in Educational Centers. The objective of this investigation was to adapt the Amotivation Inventory-Physical Education to the Spanish context, in addition to examining its psychometric properties. Method: Two hundred thirty-two boys and girls from 6th grade of Primary Education participated. Ages ranged from 10 to 12 years old (M[subscript age] = 10.99; SD = 0.47). Results: The results of the confirmatory factor analysis showed adequate model fit. In addition, the factor structure was shown to be invariant by gender. High levels of internal consistency were obtained and external validity was shown through a linear regression analysis with physical activity behaviour and physical self-concept as independent variables to explain amotivation in physical education lessons. Discussion and Conclusion: In conclusion, the scale is shown to be a reliable, gender-invariant and valid measure with both boys and girls in Primary Education.