When high pressure is applied to Ce-Al metallic glasses, their disordered atomic structure exhibits some unusual properties like polyamorphism or transformation into a crystalline phase. In this work, we probe the atomic arrangement of Ce55Al45 and Ce75Al25 glasses by X-ray absorption spectroscopy and X-ray diffraction in the pressure range of 0–30 GPa. The pressure-dependent parameters of local environment of cerium atoms are evaluated by extended X-ray absorption fine structure (EXAFS) fitting. We demonstrate that due to compositional dependence of stiffness of Ce-Al pairs, densification of Ce55Al45 is accompanied by an increase of atomic size mismatch between Ce and Al stabilizing the amorphous phase, while a decrease of the mismatch is observed in Ce75Al25 alloy which eventually leads to its devitrification at 25 GPa. Display omitted •Ce-Ce pairs are nearly equally stiff in Ce55Al45 and Ce75Al25 metallic glasses.•Ce-Al pairs are significantly more stiff in Ce75Al25 than in Ce55Al45.•On compression, Al/Ce size mismatch decreases in Ce75Al25 and increases in Ce55Al45.•Devitrification of Ce75Al25 results from a topological instability of the glass.