The invention relates to a device and a method for weighing containers (2) supplied along a conveying line (L). The device comprises: first weighing means (MP1) arranged on a first side (L1) of a stretch (T) of the conveying line (L) of containers (2) in a proximal position thereto; second weighing means (MP2) arranged at a side of the stretch (T) of the conveying line (L) of containers (2) in a distal position thereto; a supporting member (8) activatable between a first position (P1) in which it is arranged at the stretch (T) of the conveying line (L) for receiving the containers (2), a second position (P2) in which it engages with the first weighing means (MP1), and a third position (P3) in which it engages with the second weighing means (MP2); and first guide means (9) activatable between a guide configuration (C1), in which they are arranged at the stretch (T) in order to guide the containers (2) along the conveying line (L), and a disengaged position (C2). The method comprises steps of: activating the support member (8) in order to bring the containers (2) received from the conveying line (L) into the third position (P3); activating the second weighing means (MP2) order to weigh the containers (2); activating the first guide means (9) in order to reach the guide configuration (C1) in phase relation with the movement of the support member (8).