Responsibility in planning for sustainable development (SD) is little conceptualised in the planning literature. This paper sets up a theoretical framework to extend its understanding by drawing on ethics and political constructions of responsibility at their intersection with planning studies and SD debates. This is then applied to explore responsibility outlooks in planning practice in Sweden and England. It is argued that planning theory needs to further engage with the ethics of responsibility in planning but also with its politics, while the variety of responsibility landscapes in planning practice calls for a re-examination of responsibilities in planning for SD.