Although gratitude is typically conceptualized as a positive emotion, it may also induce socially oriented negative feelings, such as indebtedness and guilt. Given its mixed emotional experience, we argue that gratitude motivates people to improve themselves in important life domains. Two single-timepoint studies tested the immediate emotional and motivational effects of expressing gratitude. We recruited employees (n = 224) from French companies in Study 1 and students (n = 1026) from U.S. high schools in Study 2. Participants in both studies were randomly assigned to either write gratitude letters to benefactors or outline their weekly activities (control condition). Expressing gratitude led to mixed emotional experiences (e.g., greater elevation and indebtedness) for employees and students as compared with the control group. Students also felt more motivated and capable of improving themselves, as well as conveyed stronger intentions to muster effort towards self-improvement endeavors.