An instrument for assembling a polyaxial bone anchor is provided, the polyaxial bone anchor including a bone anchoring element (2) and a receiving part (4) that is configured to pivotably receive the bone anchoring element wherein the instrument (1, 1) includes a first member (30, 30) that is configured to engage the receiving part (4) a second member (50, 50) that is configured to contact the anchoring element (2) when it is received in the receiving part, and a position indicator (50b, 45b) that is configured to indicate the position of the anchoring element relative to the receiving part based on the position of the second member relative to the first member.
