Defect engineering is an effective method to enhance the power factor of a thermoelectric material by modulating its band structure. For cuprous delafossite oxides, the limitations in achieving an outstanding figure of merit zT are due to their intrinsically low charge carrier mobility and high thermal conductivity. Herein, we apply defect engineering via doping CuAl1-xFexO2 with x=0.05, 0.1, 0.2 at different deposition temperatures to overcome the aforementioned issues. The effects of Fe doping on both electronic properties and thermal conductivity have been systematically studied. The addition of Fe was found to enhance the electrical conductivity with an increased carrier density. The mass difference between Al and Fe resulted in phonon scattering, which significantly reduced the thermal conductivity. As a result, the ultra-low thermal conductivity of 0.776 W/m·K was obtained at 773 K for CuAl0.8Fe0.2O2. Detailed analyses of the temperature-dependent Seebeck coefficient, electrical conductivity, and thermal conductivity with materials properties have been discussed. The effect of Fe addition is advantageous for the improvement of CuAlO2 thermoelectric properties.