can allow the discovery of basic new physical phenomena and the development of new device concepts. [1] The discovery of new vdW quantum materials and their heterostructures starting from graphene, insulators, semiconductors, superconductors, and topological materials has revolutionized both fundamental and applied research. [2,3] The most recent addition to this vdW family is magnets, which have offered various advantages over conventional magnets and opened new perspectives in vdW heterostructure designs. [4][5][6] In addition to the atomically thin and flat nature of vdW magnets, flexibility, gate tunability, strong proximity interactions, and twist angle between the layers can offer a unique degree of freedom and an innovative platform for device functionalities. [4,5] Recently, several vdW magnets have emerged with the discovery of insulating Cr 2 Ge 2 Te 6 , [7] semiconducting (CrI 3 , [8] CrBr 3 [9] ), and metallic Fe x GeTe 2 . [10,11] The insulating vdW magnets are useful for spin-filter tunneling [9,12] and proximityinduced magnetism, [13][14][15] whereas the metallic magnets can be used as electrodes in magnetic tunnel junctions, [16] observationThe discovery of van der Waals (vdW) magnets opened a new paradigm for condensed matter physics and spintronic technologies. However, the operations of active spintronic devices with vdW ferromagnets are limited to cryogenic temperatures, inhibiting their broader practical applications. Here, the robust room-temperature operation of lateral spin-valve devices using the vdW itinerant ferromagnet Fe 5 GeTe 2 in heterostructures with graphene is demonstrated. The room-temperature spintronic properties of Fe 5 GeTe 2 are measured at the interface with graphene with a negative spin polarization. Lateral spin-valve and spin-precession measurements provide unique insights by probing the Fe 5 GeTe 2 /graphene interface spintronic properties via spin-dynamics measurements, revealing multidirectional spin polarization. Density functional theory calculations in conjunction with Monte Carlo simulations reveal significantly canted Fe magnetic moments in Fe 5 GeTe 2 along with the presence of negative spin polarization at the Fe 5 GeTe 2 / graphene interface. These findings open opportunities for vdW interface design and applications of vdW-magnet-based spintronic devices at ambient temperatures.