Gratitude is essential to social life and well-being. Although research with youth populations has gained momentum recently, only two gratitude interventions have been conducted in youth, targeting mostly adolescents. In the current research, we tested a new intervention for promoting gratitude among the youngest children targeted to date. Elementary school classrooms (of 8- to 11-year-olds) were randomly assigned either to an intervention that educated children about the appraisal of benefit exchanges or to a control condition. We found that children's awareness of the social-cognitive appraisals of beneficial social exchanges (i.e., grateful thinking) can be strengthened and that this, in turn, makes children more grateful and benefits their well-being in terms of increased general positive affect. A daily intervention produced evidence that this new approach induced gratitude immediately (2 days later) and led children to express gratitude more behaviorally (i.e., they wrote 80% more thank-you cards to their Parent--Teacher Association). A weekly intervention induced gratitude up to 5 months later and additionally showed an effect on well-being (i.e., positive affect). Evidence thus supported the effectiveness of this intervention. Results are discussed in terms of implications for positive youth development and academic functioning.