Background　and　Purpose:　Functional　outcome　after　stroke　may　be　related　to　preexisting　brain　health.　Several　imaging　markers　of　brain　frailty　have　been　described　including　brain　atrophy　and　markers　of　small　vessel　disease.　We　investigated　the　association　of　these　imaging　markers　with　functional　outcome　after　acute　ischemic　stroke.　Methods:　We　retrospectively　studied　patients　with　acute　ischemic　stroke　enrolled　in　the　AXIS-2　trial　(AX200　in　Ischemic　Stroke　Trial),　a　randomized　controlled　clinical　trial　of　granulocyte　colony-stimulating　factor　versus　placebo.　We　assessed　the　ratio　of　brain　parenchymal　volume　to　total　intracerebral　volumes　(ie,　the　brain　parenchymal　fraction)　and　total　brain　volumes　from　routine　baseline　magnetic　resonance　imaging　data　obtained　within　9　hours　of　symptom　onset　using　the　unified　segmentation　algorithm　in　SPM12.　Enlarged　perivascular　spaces,　white　matter　hyperintensities,　lacunes,　as　well　as　a　small　vessel　disease　burden,　were　rated　visually.　Functional　outcomes　(modified　Rankin　Scale　score)　at　day　90　were　determined.　Logistic　regression　was　used　to　test　associations　between　brain　imaging　features　and　functional　outcomes.　Results:　We　enrolled　259　patients　with　a　mean　age　of　69　+/-　12　years　and　46　%　were　female.　Increased　brain　parenchymal　fraction　was　associated　with　higher　odds　of　excellent　outcome　(odds　ratio　per　percent　increase,　1.078　[95%　CI,　1.008-1.153]).　Total　brain　volumes　and　small　vessel　disease　burden　were　not　associated　with　functional　outcome.　An　interaction　between　brain　parenchymal　fraction　and　large　vessel　occlusion　on　excellent　outcome　was　not　observed.　Conclusions:　Global　brain　health,　as　assessed　by　brain　parenchymal　fraction　on　magnetic　resonance　imaging,　is　associated　with　excellent　functional　outcome　after　ischemic　stroke.　Registration:　URL:　.　Unique　identifier:　NCT00927836.