A magazine loader comprises a body for receiving an upper portion of the magazine and a cap slidingly engaged with the body for loading cartridges in to the magazine received by the body. The body comprises a plurality of wall portions defining a body cavity configured to receive an upper portion of a magazine. The plurality of cap wall portions may comprise a starboard cap wall portion and an opposing port cap wall portion. An upper portion of the body is slidingly received in the interior volume defined by the cap so that the body and the cap slide relative to one another along a sliding axis. The sliding axis may extend in the upward and downward directions and the cap may translate between an upper position and a lower position along the sliding axis.