An implantable electrical stimulation lead includes an integrated fixation mechanism that expands upon implantation of the lead to fix the lead relative to a target tissue site, such as tissue within the epidural region proximate the spine or the sacral foramen. The fixation mechanism may include one or more expandable wire-like elements, which may be configured in a substantial helical shape. The wire-like elements may be formed from an elastic or super-elastic material, and expand radially outward when a restraint mechanism is removed following implantation of the lead.
