TP91 steel was obtained by wire arc additive manufacturing (WAAM). The TP91 heat-resistant steel possessed good forming morphology. Its main metallographic structure was sorbite. Fluctuations of the microhardness were small with the corresponding average values equal to 219 and 216 HV_0.2, respectively. The TP91 heat-resistant steel also exhibited excellent mechanical properties at 20 ºC and 600 ºC. Its room temperature longitudinal yielded strength and tensile strength values, as well as the elongation, were equal to 817 and 885 MPa and 12.5%, respectively. The same values in the transverse direction were equal to 801 MPa, 880 MPa, and 13.5%, respectively. The Charpy impact values obtained at 20 ºC for the longitudinal and transverse directions were equal to 147 and 152 J, respectively. At 600 °C, longitudinal and transverse yield and tensile strengths, as well as elongation, were equal to 281 and 274 MPa, 325 and 316 MPa, and 16% and 20%, respectively.