The　formation　of　second-phase　particles　by　solid-state　precipitation　is　well-known　as　the　most　effective　strengthening　method　for　the　light-weight　aluminum　(Al)　alloys.　Here,　the　interfacial　evolutions　from　Sc　solute　segregation　to　Al3Sc　precipitation　at　θ′-Al2Cu/matrix　interfaces　were　investigated　in　an　Al–Cu–Sc　alloy　crept　at　beyond　300　°C.　By　considering　the　trace　Si　impurity,　it　is　proposed　that　Al3Sc　precipitation　preferentially　occurs　at　the　Si-concentrated　interfacial　locations,　i.e.　growth　ledges.　Two　effects　of　interfacial　Al3Sc　precipitation　on　θ′-Al2Cu　were　demonstrated:　(1)　The　Al3Sc　precipitation　was　processed　at　the　expense　of　the　adjacent　Sc　segregation　and　allows　localized　θ′-Al2Cu　decomposition,　causing　＇precipitate　splitting＇.　(2)　The　Al3Sc-enclosed　growth　ledges　resultantly　prevented　θ′-Al2Cu　from　coarsening　and　equilibrium　transformation　to　θ-phase　at　temperature　as　high　as　400　°C.　This　work　is　expected　to　provide　a　precipitate-stabilizing　strategy　by　interfacial　architecture　to　maintain　the　closely　spaced　dispersion　of　precipitates　and　its　strengthening　contribution　at　elevated　temperature.　©　2020　Elsevier　B.V.