(1) Background: The aim of the present study is to analyze subjective happiness in relation to leisure time in 10-year-old boys and girls from Brazil, Chile and Spain and to determine which leisure time activity has a greater effect on their subjective happiness and whether there are differences according to gender. (2) Methods: Data from the third wave of the Children’s Worlds Project was used, which was collected by administering self-report measures to representative samples in each country. The sample was composed of 4008 early adolescents from Brazil (22.1%,n= 886), Chile (22.8%,n= 913) and Spain (55.1%,n= 2209). The mean age of the sample was 10.17 years (SD = 0.57), and 51.7% were girls. (3) Results: In terms of subjective happiness, moderate to high means were observed, with higher scores in boys and the Spanish sample. The results showed some differences in leisure time activities among children from Brazil, Chile and Spain. Furthermore, the results highlighted the importance of relaxation time with the family to promote happiness in pre-adolescence across genders and countries. Additionally, playing outdoors and doing homework were also found to be protective factors for subjective happiness. (4) Conclusions: In Brazil, Chile and Spain the most consistent result was the positive effect of spending time relaxing with the family on subjective happiness.