Aneuploidy is found in most solid tumours, but it remains unclear whether it is the cause or the consequence of tumorigenesis. Using Plk4 overexpression (PLK4OE) during epidermal development, we assess the impact of centrosome amplification and aneuploidy on skin development and tumorigenesis. PLK4OE in the developing epidermis induced centrosome amplification and multipolar divisions, leading to p53 stabilization and apoptosis of epidermal progenitors. The resulting delayed epidermal stratification led to skin barrier defects. Plk4 transgene expression was shut down postnatally in the surviving mice and PLK4OE mice never developed skin tumours. Concomitant PLK4OE and p53 deletion (PLK4OE/p53cKO) rescued the differentiation defects, but did not prevent the apoptosis of PLK4OE cells. Remarkably, the short-term presence of cells with supernumerary centrosomes in PLK4OE/p53cKO mice was sufficient to generate aneuploidy in the adult epidermis and triggered spontaneous skin cancers with complete penetrance. These results reveal that aneuploidy induced by transient centrosome amplification can accelerate tumorigenesis in p53-deficient cells.