This work aims to investigate the use of active thermography on welded joints, a non-destructive method which is required if verifications are carried out on working components. Unlike the traditional method, where the workpiece is thermally stimulated by a laser beam at the end of the process, the method here adopted is based on real-time control of welding. By means of a thermal imaging camera, in fact, data collection takes place simultaneously with the welding itself, leading to a considerable reduction in time and consequently in costs. Thanks to Ades Group, at their site in Rovato (BS), four welding tests, monitored by an infrared camera, were carried out to analyze the different behavior of S275JR steel depending on welding method (SMAW and GMAW), material thickness (3mm and 5mm) and type of joint (butt joint and tee joint).