The invention relates to a seat assembly, which is intended particularly for assisting a person sitting thereon to stand up from a sitting position and, which comprises a seat part (1) provided in connection with a sitting base (A) and equipped with elbow rests (la), wherein in connection with the seat part (1) are arranged tilting means (2) in order to incline the seat part (1) from an essentially horizontal sitting -position (I) to a standing up -position (II), where the seat part is inclined downward toward its front edge, and lifting means (4) in order to move the seat part (1) upward while being inclined to the standing up-position (II) from the sitting -position (I), the tilting means and lifting means operating simultaneously through a joint mechanism, whereby particularly in order to enable assisting a standing up -movement by influence of the person him-/herself sitting on the seat part (1), by exploiting his/her upper body through using hand force, a joint mechanism (2, 4) functioning on a quadrangle joint -principle is arranged operable at least partly through the elbow rests (la), such as by a power influence (F) directed downward from the elbow rests (1a) essentially in front of a turning joint (N ) for a tilting and lifting movement (w).
