Immigration to western countries is a relevant phenomenon that has been linked to health inequalities. One form of inequality is ethnocentrism in health programmes. Therefore, social innovations and a new transcultural approach have been developed to culturally adapt health education interventions. This study aimed to evaluate the effects of a double transcultural health intervention, the Leader Adolescents in Transcultural Health Education (LATES) Project, which is led by high school immigrant adolescents over elementary students of multicultural contexts in southeastern Spain. This double quasi-experimental study had experimental and control groups composed of secondary students (12 health cultural brokers with 36 controls) and elementary students (26 participant students and 26 controls). The LATES Project was delivered to two high schools and two elementary schools in Almeria (Spain). A mixed evaluation method was used. Six attitudinal scales were used pre- and post-intervention to collect the data. The quantitative evaluation was completed using qualitative techniques through in-depth interviews and focal groups. Four sociocultural gradients were identified pre-intervention: a positive rural gradient, a negative gender gradient except in traditional ‘female’ dimensions, a negative age gradient and a dual migrant gradient that combined the health migrant effect in some behaviours and westernization in others. Specifically, the Moroccan population demonstrated better attitudes towards eating and physical activity behaviours. After the intervention, the experimental groups showed more improvement than the controls. However, the attitudinal scale increment is modest compared with the knowledge and motivation improvements. This intervention, which used a transcultural approach, has benefited young Spaniards to a greater extent than immigrants, probably due to the worse initial health conditions of the Spanish.