Online reviews can make or break a mobile app. Various studies have shown that reviews, especially when their valence is primarily positive, can contribute to the survival of a particular app in a stiffly competitive market. Hence, it is in the best interest of app developers to gain insights into the motivations of app users to review apps they have used. To address the question on the factors influencing people’s intention to write reviews for apps, an extended version of the Theory of Planned Behavior (with the inclusion of various writing functions as predictors) was tested with data from 203 German mobile app users. Results of structural equation modeling reveal that people’s intention to review certain apps is a function of four factors, namely their attitude towards writing reviews, subjective norm, and review writing’s ego-defensive and emotional expression functions. Furthermore, both review writing’s ego-defensive and emotional expression functions positively influence app users’ attitude towards writing reviews.