A fixation device for retaining a leadless medical implant to tissue includes an annular collar and an array of self-expanding tines extending from the collar. When deployed, the annular collar encircles the implant and the tines are preset to splay outwardly from the implant to grab body tissue and anchor the implant at a treatment site. The implant and fixation device are contained within a sheath for delivery to the treatment site and a pushing force is applied to a pusher of the delivery system to distally advance the fixation device relative to the implant and deploy the tines. A distal end of the implant having an electrode may form a distal tip of the delivery system, and a potential implantation site may be tested prior to deployment of the fixation device to allow for easy repositioning of the implant if the potential implantation site is determined to be unacceptable.