The invention relates to a backrest (1) intended to be connected to a wheelchair frame (2) includes a first lateral end (11), a second lateral end (12), a front side (13) and a back side (14), at least one pair of side wings (3,4), namely a first side wing (3) and a second side wing (4), that may be generally vertically oriented when connected to the wheelchair frame (2), and connecting means (10) configured to fixedly connect the first side wing (3) and the second side wing (4) to the wheelchair frame (2). The first side wing (3) comprises a plurality of vertically spaced first transverse profiles (5) extending therefrom towards the second side wing (4) and the second side wing (4) comprises a plurality of vertically spaced second transverse profiles (6) extending therefrom towards the first side wing (3). At least one first transverse profile (5) of the first side wing (3) and at least one associated second transverse profile (6) of the second side wing (4) are at least partially mutually embraced in a slidable manner. The at least one first transverse profile (5) and the at least one second transverse profile (6) are dimensioned and configured so that the mutual slidably embracement of the at least one first transverse profile (5) and the at least one second transverse profile (6) is made on a range of distances enabling the width adjustment of the backrest (1). The mutual embracement of the at least one first transverse profile (5) and the at least one second transverse profile (6) are configured to prevent the side wings (3,4) from disengaging from each other in a direction other than the slidably direction of the side wings (3,4). The first transverse profiles (5), respectively the second transverse profiles (6), are at least partially linked together so as to define approximately a continuous surface (S c).
