This study aims to compare personal relationships satisfaction and subjective well-being of Brazilian and Spanish children and to verify if personal relationships are associated with subjective well-being for the sample. Participants are 6,747 children aged from 11 to 14 years old (M = 12.07, DP = 0.731), 1,020 being Brazilian and the others Spanish. From the total sample 50.7% were girls. Results pointed that the items of personal relationships are grouped into three components related to family, school and friends. Spanish children had higher means than Brazilians' in the items of personal relationships and in the subjective well-being scale. There is a significant association between personal relationships and subjective well-being, and the relationships with family, school and friends are predictors of children well-being in both countries. Family relationships are those with the highest contribution to the prediction of child well-being for both countries, followed by relationships at school and with friends. Personal relationships can be considered a predictor of child well-being with approximately 40% of explained variance for both countries.