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A new set of physical property measurements was undertaken on 29 peak‐ring samples from the IODP‐ICDP Expedition 364. Among the studied lithologies, the dominant one recovered in the peak ring consists of shocked granitoid rocks (19 samples). Porosity measurements with two independent methods (triple weight and 14C‐PMMA porosity mapping) concur and bring new observations on the intensity and distribution of fracturing and porosity in these shocked target rocks. Characterization of the porous network is taken a step further with two other independent methods (electrical and permeability measurements). Electrical properties such as the cementation exponent (1.59 < m< 1.87) and the formation factor (21 < F< 103) do not compare with other granites from the published literature; they point at a type of porosity closer to clastic sedimentary rocks than to crystalline rocks. Permeabilities of the granitoid rocks range from 0.1 to 7.1 mD under an effective pressure of ∼10 MPa. Unlike other fresh to deformed and altered granitoid rocks from the literature compared in this study, this permeability appears to be relatively insensitive to increasing stress (up to ∼40 MPa), with implications for the nature of the porous network, again, behaving more like cemented clastic rocks than fractured crystalline rocks. Other analyzed lithologies include suevite and impact melt rocks. Relatively low permeability (10−3mD) measured in melt‐rich facies suggest that, at the matrix scale, these lithologies cutting through more permeable peak‐ring granitoid rocks may have been a barrier to fluid flow, with implications for hydrothermal systems. Sixty‐six million years ago, a 10–15 km sized meteorite ended its trajectory on Earth. The resulting crater, Chicxulub, is still preserved to this day in Mexico. The impact had dramatic consequences on Earth's organisms. Drilled core samples from its peak ring help to better understand what are the physical mechanisms involved in such large impact events, on Earth and other planets. This study looks at how the rocks shocked during the impact have been affected, they consist principally of granites. Intact granites are crystalline rocks known to have low porosity (<2%), typically resulting from microscopic cracks. Granites recovered from the crater have higher porosities (∼10%) and are so densely cracked that they behave more like a sandstone than cracked crystalline rocks. This observation results from physical measurements, presented in this paper, that also suggested that fluid can flow relatively easily in these granites, with implications for hydrothermal systems and life in the aftermath of the impact. Independant petrophysical measurements are used to caracterize the nature of the porosity in Chicxulub impact crater's peak ringShocked granites behave more like a cemented clastic rock than a fractured crystalline rockMatrix permeabilities of peak‐ring lithologies bring new insight on fluid flow in postimpact hydrothermal systems Independant petrophysical measurements are used to caracterize the nature of the porosity in Chicxulub impact crater's peak ring Shocked granites behave more like a cemented clastic rock than a fractured crystalline rock Matrix permeabilities of peak‐ring lithologies bring new insight on fluid flow in postimpact hydrothermal systems