<p>This study examines the combined effects of Arctic and ENSO thermal conditions on Eurasian winter mean and extreme temperatures and the underlying mechanisms, using reanalysis data and CMIP6 model outputs. Results show that the cold Barents-Kara Seas (BKS) troposphere is more prevalent during neutral ENSO winters, favouring a warm Eurasian winter. In contrast, warm BKS is typically observed during La Niña winters, leading to pronounced and extensive cooling in the Eurasian midlatitudes. The negative Pacific-North America (PNA) wave train stimulated by La Niña propagates northeastward to North America and the Canadian Archipelago, amplifying the BKS warming and extending the Eurasian wave train to midlatitude Eurasia. Simultaneously, another branch of wave train spliting from the PNA traverses the Atlantic Ocean to reach the Eurasian continent along the accelerated subtropical jet stream. During El Niño winters, cold and warm BKS events occur with equal probability. Although the El Niño doesn’t change the Eurasian winter-mean temperature much, it appears to increase the frequency of extreme cold events due to the westward extension of the strengthened Aleutian low-pressure system. When combined with cold Arctic conditions, it modulates the midlatitude cold extremes through the PNA teleconnection and the North Atlantic Oscillation, leading to more frequent and colder extremes. Generally speaking, the physical mechanism behind the combined effects is mainly the contribution of tropospheric pathways, with the stratospheric pathways playing a minor role. This study highlights the critical role of differing Arctic and ENSO combinations in determining the Eurasian midlatitude winter temperature, which are of significant implications for the attribution and prediction of cold extremes.</p>