The present invention relates to a device for supporting a pair of wiper blades (12, 26; 13, 27), comprising first and second supporting grooves (14, 28), each of which is provided with a means for retaining at least one laterally extending structural element (22; 54) of two respective blades (12, 26; 13, 27) by resilient nesting. According to the invention, the supporting grooves (14, 28) are arranged side by side with a common wall, the supporting grooves having two respective openings leading into parallel and offset planes (R1, R2), the second supporting groove (28) being arranged above the first supporting groove (14) and having a substantially flared shape, wherein said openings belong to a single side of the supporting device. The present invention also relates to a supporting assembly comprising a plurality of supporting devices, and to a corresponding mounting method.