In February 2022, Russia launched its full-scale invasion of Ukraine. This decision forced the European Union (EU) and the North Atlantic Treaty Organisation (NATO) to take more decisive action in supporting Ukraine’s defence of its territory. For example, many EU member states increased their defence spending and sent weaponry to Ukraine. However, the interoperability issue remains pertinent as the European Defence and Technological and Industrial Base (EDTIB) is structurally fragmented. Moreover, given Ukraine’s inheritance of Soviet-era weaponry, further training and logistical difficulties have arisen, posing setbacks and challenges to Ukraine’s effective defence strategies. This paper will discuss the joint action of the EU and NATO and its impact on Ukraine’s defence of its territory. The analysis will focus on the evolution of financial mechanisms and the creation of a military mission on the ground that complements nonmilitary efforts. Following this, it explores NATO’s complementary action, reinforcing cooperation with Ukraine and boosting armament in the East. Finally, the paper analyses hybrid threats in the examined case and problematises about a way forward through EU-NATO joint action.