The present study aimed to examine the significance of young Portuguese people's experiences of participating in a global Catholic event, the World Youth Day, by discussing their motivations and learning opportunities. World Youth Day is seen as a major experience full of many small experiences that become part of the lifelong process of socialisation. These may include non-formal and informal educational experiences. The literature has pointed to the religious/spiritual significance of the event, but other aspects have yet to be studied. The present study used a mixed-methods methodology that included a questionnaire (N = 1,351) and 20 semi-structured interviews, to Portuguese young people participating in the event. The results showed that the religious/spiritual dimension was important as motivations and effects, but cultural and social aspects were also very relevant. Membership of a Catholic youth group was crucial in the decision to participate and to the process of learning to live with others. The Pope appeared as a central figure in the event, and the way he communicated with participants enhanced their sense of belonging to the Catholic Church.