Abstract: Family and research are very important for most people. They have a huge impact on individual happiness. The relationship between research family balance and happiness has received considerable importance in positive psychological research. The aim of this present study was to examine whether self-esteem mediates the relationship between research family balance and happiness among working mothers. The subjects of the study were 526 working mothers with children and working husband. The data were collected using work-family balance, self-esteem and happiness scales. The correlation coefficients indicated that work-family balance relates to self-esteem and happiness while self-esteem relates to happiness. An analysis using Structural Equation Modeling (SEM) showed that self-esteem partially mediates the relationship between work-family balance and happiness. This study has implications for working mothers who seek new way to promote happiness. The limitations of the research are discussed.