Welding is one of the most important industrial processes in engineering and construction sectors due to its vital role in joining metals and ensuring their performance. Even tough, the mechanical and structural properties of metals after welding are directly affected by the cooling method, improper cooling may cause distortions or internal stresses that weaken durability. This study aims to investigate the effect of different cooling methods on the microstructure of low-carbon steel (0.2% C) after arc welding, the welded samples were cooled in three media (air, water, oil) and then examined using non-destructive tests, microscopic analysis, and hardness measurements. The results showed that rapid water cooling increased surface hardness but caused significant internal stresses and non-uniform distribution of ferrite and pearlite. Oil cooling provided a relative balance between hardness and toughness, yet the microstructural details were less clear. In contrast, slow air cooling provides most effective result, it is producing a uniform ferrite–pearlite structure and minimizing internal stresses, despite slight surface oxidation. The study concludes that air cooling is the optimal method for preserving the crystalline structure and mechanical properties of low-carbon steel after welding, while oil cooling may be considered an alternative cooling method. The study recommends broadening the scope of future research to encompass advanced analyses employing more precise microscopic techniques, as well as examining the influence of intermediate or hybrid cooling rates, and establishing correlations between the obtained results and the corresponding mechanical properties................. Keywords:............... cooling rate, microstructure, heat-affected zone, rapid cooling.