Carbon fiber reinforced carbon composites (Cf/C) were first joined by combining electric field-assisted sintering technology and using a Ti3SiC2 (TSC) tape film as interlayer. A joint with shear strength of 26.3 ± 1.7 MPa was obtained within 12 min at a joining temperature of 1200 °C. The joint morphology, interface reaction, shear fracture behavior, and joining mechanism were investigated in detail. To achieve reliable joining of a Cf/C composite to itself via a TSC interlayer, the current work show the crucial controlling factor of interface reaction on the shear strength and the shear fracture behavior. Optimized bonding could be achieved without sacrificing the high strength of the carbon fibers and also taking advantage of the pseudo-plasticity feature of the TSC interlayer. A possible high-toughness joining structure was also proposed based on these results. The current-aid joining technique shortened significantly the bonding process of the Cf/C composites at moderate temperatures, and simplifies the manufacture of components with complex shapes.