Subcutaneous implantation tools and methods of implanting a subcutaneous device using the same. The tool may include a tool body having a longitudinally extending recess having a distal opening and having a tunneler at a distal end of the tool body extending from the distal opening of the recess. The tool may include a plunger slidably fitting within at least a portion of the tool body recess. The recess may be configured to receive an implantable device and the tunneler preferably extends distally from the recess at a position laterally displaced from the device when the device is so located in the recess. Movement of the plunger distally within the recess advances the device distally out of the recess and alongside of and exterior to the tunneler.