The purposes of this study were to analyze individual interviews about how young children perceived the meanings of happiness and when they felt happy, to understand the characteristics of their thoughts and experiences of happiness, and to make plans to promote their happiness. The subjects included 274 young children aged 3-5 at two kindergartens and one daycare center in Seoul. The findings were as follows: first, young children explained the meanings of happiness with positive emotional states such as feeling good, loving, feeling glad, liking, having fun, and excited. A considerable number, however answered that they didn’t know. Secondly, young children felt happy when engaging in their favorite play, being together with their favorite person, having emotional supports, receiving presents, going to some special place, having their favorite food, their body and mind felt comfortable, and achieving what they wanted through efforts. Happiness is an essential factor for good and full life. It is necessary to provide young children with happy experiences so that they can maintain a happy life. There is a need for education to help them realize that true happiness comes from taking an interest in and making a contribution to the happiness of others beyond the pursuit of personal happiness and to increase their power of execution.