The use of high-strength sheet material applications in the automotive industry has become widespread due to their high strength/weight ratios. The formability, however, of these high-strength sheet materials is limited at room temperatures (RTs). In this study, the first of its kind to be conducted, experimental research was performed on the formability of HC420LA grade sheet material using the warm deep drawing (WDD) method. Temperature control is the most important parameter in WDD. In this method, a new temperature control system was designed and manufactured to increase the formability of HC420LA grade sheet material. The limiting drawing ratio (LDR) for a 1.2-mm sheet thickness of HC420LA grade sheet material, which is 2.14 at RT, increased to 2.47 after applying this method. For a 1.5-mm sheet thickness of HC420LA, LDR, which is 2.15 at RT, increased to 2.59 after applying this method. Percent increases of the drawing ratios for 1.2 and 1.5 mm thicknesses were 15.42 and 20.45 %, respectively. A maximum reduction of 15 % in thickness was obtained in formed cups. Lastly, the microstructures of the warm cup's punch corner region and wall and bottom regions were investigated under an optical microscope. The results showed whether any changes occurred in the microstructures and mechanical properties.