We demonstrate Fourier domain optical coherenc tomography (FDOCT) monitoring and guiding of quantum cascade laser (QCL) therapy. The laser therapy is performed with a 6.1-μm mid-IR QCL and it involves both tissue coagulation or ablation. FDOCT allows real-time monitoring that minimize unnecessary damage to the surrounding tissues. We perform lipid phantom tissue ablation, chicken egg yolk coagulation, and tissue and blood vessel coagulation on chicken embryo to validate the FDOCT guiding quantum cascade laser therapy.