A polyaxial bone anchoring device is provided includinga bone anchoring element (1) comprising a shank (2) for anchoring to a bone and a head (3)；a receiving part (5, 5', 5") comprising a first end (5a), a second end (5b), a longitudinal axis (C) extending through the first end and the second end, a channel (53) at the first end for receiving a rod, and an accommodation space (52) for pivotably holding the head (3)；a pressure member (6, 6',6") configured to be positioned in the receiving part (5, 5', 5") and to exert pressure onto the head (3) to lock the head in the receiving part, the pressure member comprising a pressure exerting surface and a deformable portion (66a, 66b； 66a', 66b'； 66a", 66b") comprising a free end (67), wherein the deformable portion is configured to assume at least a first configuration and a second configuration, and wherein the pressure member is movable along the longitudinal axis from an insertion position to a locking position； anda rod (100) configured to be inserted into the channel (53) and to move in the channel along the longitudinal axis (C) and to exert a force onto the deformable portion of the pressure member (6； 6',6")；wherein, when the head (3) is in the receiving part, and when the deformable portion (66a, 66b； 66a', 66b'； 66a", 66b") of the pressure member is in the first configuration and the rod is in contact with the deformable portion at a first axial position relative to the receiving part, the free end (67) of the deformable portion is supported by the receiving part and the rod (100) is movable towards the head (3) to exert a force on the deformable portion for adjusting the deformable portion from the first configuration to the second configuration.
