Smart Cities consist of a multitude of interconnected devices and services to, among others, enhance efficiency, comfort, and safety. To achieve these aims, smart cities rely on an interplay of measures including the deployment of interventions targeted to foster certain human behaviors, such as saving energy, or collecting and exchanging sensor and user data. Both aspects have ethical implications, e.g., when it comes to intervention design or the handling of privacy-related data such as personal information, user preferences or geolocations. Resulting concerns must be taken seriously, as they reduce user acceptance and can even lead to the abolition of otherwise promising Smart City projects. Established guidelines for ethical research and practice from the psychological sciences provide a useful framework for the kinds of ethical issues raised when designing human-centered interventions or dealing with user-generated data. This article thus reviews relevant psychological guidelines and discusses their applicability to the Smart City context. A special focus is on the guidelines’ implications and resulting challenges for certain Smart City applications. Additionally, potential gaps in current guidelines and the limits of applicability are reflected upon.