Abstract: A walker (1) with a mechanism for assisting a user (21) in standing and sitting operations, comprising a support structure equipped with movement means (2,3), a device (20) for securing the user to the walker and a system for blocking the movement means, wherein the support structure comprises at least one pivoting arm (14) that guides the device (20) for securing the user (21), a guide support (11) that is fixed to the walker (1) and guides the arm (14), and a control module (15) that controls the system for blocking the movement means (2,3) and which comprises means for selecting a working mode of the walker, by selecting from between “walking mode” and “sitting/standing mode”.