Children's happiness at school has been mainly investigated from a quantitative perspective, largely overlooking what children understand by happiness and whether their conceptualizations are shaped by culture. Hence, in the present study, using a quantification of qualitative data, we investigated whether English (n = 421, M = 10.63 years, 223 girls) and Spanish (n = 223, M = 11.13 years, 112 girls) children reported different conceptualizations of happiness at school. Results showed that English children defined happiness at school as experiencing autonomy, non-violence, and having a positive relationship with teachers. On the other hand, Spanish children mentioned more harmony and having leisure time, as compared to English children. Finally, compared to boys, girls mentioned more in their definitions emotional support, having a positive relationship with teachers, and experiencing competence. The obtained findings are discussed in light of previous well-being literature taking into account the role of culture and the school context in both countries.