Despite the performance improvement in perovskite solar cells (PSCs) when MXenes are employed as transport layers, device stability studies are still missing. Especially under real outdoor conditions where devices are subjected to the synergy of multiple stressors. In this work, functionalized 2D titanium carbide (Ti3C2) MXene is employed in normal PSC configuration, at the interface between the halide perovskite and the hole transport layer. The functionalization of the Ti3C2 MXene is made utilizing the same organic additive passivating the halide perovskite layer. The functionalizing strategy creates a continuous link between the MXene and the halide perovskite layer. Champion MXene-based PSCs revealed a approximate to 22% efficiency, in comparison with the control device showing 20.56%. Stability analyses under ISOS protocols under different conditions (dark, continuous light irradiation and real outdoor analysis) reveal that the enhancement of the PSCs lifespan is always observed when the MXene layer is employed. Analysis under continuous light irradaition (ISOS-L) reveal an almost 100% retention of the efficiency for the MXene-modified device, and outdoor testing (ISOS-O) carried out for > 600 h reveals a T(80 )of approximate to 600 h, while the control device degrades completely. To the best of the authors knowledge, this is the first report of the stability assesment of MXene-based PSCs carried out under real outdoor (ISOS-O) conditions.