Alien plant invasions are a crucial yet often underestimated component of desertification processes in Spain. Their ecological and socio-economic impacts are increasingly evident, involving both species with a long history of introduction (e.g., Arundo donax) and those more recently introduced (e.g., Cenchrus setaceus). For example, invasive alien plants threaten native biodiversity, reduce the productivity of agricultural and grazing lands, and alter key ecosystem processes such as water availability, soil stability, and fire regimes. In Spain’s arid and semi-arid landscapes, where natural resilience is already compromised, the invasion of alien plants can accelerate land degradation and exacerbate desertification. Furthermore, their interaction with other global change factors can create feedback loops that further destabilize these fragile ecosystems. Integrating the management of invasive alien plants into broader environmental and restoration programs is essential to prevent further degradation and to maintain ecosystem services and supporting local communities dependent on these vulnerable drylands. Effective management can thus play a pivotal role in mitigating desertification and fostering long-term ecological sustainability in Spain.