A coupler or connector for joining bars, for example reinforcing bars, comprising an elongate rod member adapted to be inserted into a tubular sleeve member. The rod and sleeve members each have one or more transverse holes which align when the rod member is inserted into the sleeve member. In operational use, the rod and sleeve members are attached to the free ends of the bars to be connected. One or more transverse pins are then driven into the holes which are aligned in order to lock the rod and sleeve member together thereby connecting the bars. In another example of the invention, the pins can be spring loaded and/or the elongate rod member is adapted to be inserted into a pair of opposed sleeve members. In yet another example of the invention, there can be a plastic sleeve adapted to retain the pins in position thereby locking in place the sleeve and rod members. In another version where the pins are spring loaded, the plastic sleeve is slid off during assembly to allow the pins to engage the holes in the sleeve member(s).