Carbon fiber reinforced polymers (CFRPs) are widely utilized across various industries due to their exceptional mechanical properties and lightweight characteristics. Consequently, the demand for CFRPs is rising, leading to an increase in CFRP waste. This study investigates methods for recycling carbon fibers separated from waste CFRPs through chemical treatments and incorporating them into the concrete industry. First, the compressive and flexural tensile behaviors of concrete mixed with recycled carbon fibers were examined, considering the variables of fiber length and fiber volume fraction. As the length and volume fraction of recycled carbon fibers increased, the flexural tensile strength increased, up to 34%, while the compressive strength and residual tensile strength did not increase significantly. Second, the printing quality, buildability, and shrinkage characteristics before hardening were examined by incorporating recycled carbon fibers into 3D printing mortar, and the compressive strength, flexural tensile strength, and interlayer bond strength characteristics were examined after hardening. A 0.5% volume fraction of recycled carbon fibers improved the printing quality and buildability of the 3D printing mortar and reduced the 24-h shrinkage by 30%. Additionally, the 28-day compressive strength and flexural tensile strength of the 3D printing mortar increased by 19% and 16%, respectively, with no change observed significantly in the interlayer bond strength.