Described are methods and apparatuses for delivering fistula plugs into fistulae having at least a primary fistula opening, a secondary fistula opening, and a fistula tract extending therebetween. Illustratively, some inventive methods involve delivering a fistula plug into a fistula tract through a primary fistula opening and toward a secondary fistula opening, while others involve delivering a fistula plug into a fistula tract through a secondary fistula opening and toward a primary fistula opening. In certain aspects, a fistula plug is pushed and/or pulled through a fistula tract along a guidewire or other plug-guiding device, potentially protected by a protective delivery device such as a sheath, capsule or other suitable delivery vehicle.