Apparatuses and methods for in situ thermal treatment for PBF systems are provided. An apparatus for a PBF-based 3-D printer can include a heating element for heating a gas, wherein the heated gas is delivered via at least one port of the 3-D printer to conduct heat treatment on a build piece during printing. A method for thermal treatment in a PBF-based 3-D printer can include heating a gas and delivering it via at least one port of the 3-D printer arranged proximate a build piece to conduct heat treatment during printing. An apparatus for a PBF-based 3-D printer can include a temperature-regulating element for changing a temperature of a gas, at least one channel for delivering the gas to a plurality of ports, and a controller for determining gas temperatures and durations of application of the gas via different ones of the plurality of the ports.