The invention relates to a synchronizing mechanism for a correlated seat-backrest movement of an office chair, said mechanism including a base support (1) that can be placed on a chair column, a seat support (3) and a backrest support (4). In order to provide a synchronizing mechanism, by means of which a high level of seating comfort can be achieved in an inexpensive manner, a mechanism is proposed where the backrest support (4) is connected to the base support (3) so as to be pivotable about a transverse axis (8) and has an entrainment means (9) that is in operative connection with the seat support (3) in such a manner that when the backrest carries out a pivoting movement (6) backward, the seat support (3) also performs a movement (13) backward.