A lens arrangement for a monitoring camera and a monitoring camera including a lens arrangement is provided. The lens arrangement includes a lens member having a connection portion with an outer thread, an adjustment member having a through hole for receiving the connection portion and an inner thread corresponding to the outer thread, a holder member having a receiving portion for receiving the connection portion and an inner thread corresponding to the outer thread. The lens arrangement is assembled by the connection portion being screwed into the through hole and further into the receiving portion. The receiving portion has a top engagement surface and the adjustment member has a bottom engagement surface. The adjustment member is movable relative to the holder member by screwing between non-engaging and engaging states. In the engaging state, the bottom engagement surface wedgingly engages with the top engagement surface for locking the lens member.