A zero-degree assistant's device for a microscope has a tube carrier (2) for the principal observer's tube, an interface (5) for the microscope body, an assistant's module (6), pivotable about an axis (4), having an interface (7) for an assistant's tube, and having a retaining device (8, 12) for releasing and immobilizing the assistant's module (6), the tube carrier (2) for the principal observer's tube being mounted tiltably about a rotation axis (10) in such a way that tilting of the tube carrier (2) for the principal observer's tube into a tilted position makes possible unrestricted pivoting of the assistant's module (6).