Circular　concrete-filled　steel　double-tube　(CFSDT)　columns　have　shown　excellent　ductility　and　load-carrying　capacity.　However,　research　on　the　fire　resistance　of　CFSDT　columns　is　still　limited.　This　paper　presents　the　fire　tests,　finite　element　(FE)　modeling,　behavior,　and　design　of　circular　CFSDT　columns　and　concrete-filled　steel　double-skin　(CFSDS)　columns　exposed　to　fire.　The　fire　resistance　tests　of　one　CFSDS　and　six　CFSDT　columns　are　described.　Analysis　is　given　on　the　effects　of　the　material　strength,　the　thickness　of　the　inner　steel　tube,　and　the　load　ratio　on　the　fire　resistance　of　the　specimens.　Finite　element　models　are　developed　that　simulate　the　fire　behavior　of　filled　composite　columns　with　double　tubes　and　are　verified　by　fire　test　results.　The　verified　FE　models　are　employed　to　undertake　parametric　studies　on　the　structural　responses　of　CFSDS　and　CFSDT　columns　under　fire　exposure.　A　design　model　is　proposed　for　calculating　the　fire　resistances　of　CFSDT　columns.　The　results　show　that　the　load　ratio　and　the　column　slenderness　ratio　have　the　most　significant　effect　on　the　fire　resistance　of　CFSDT　columns;　the　cross-sectional　parameters　remarkably　affect　the　fire　resistance;　and　the　material　strength　has　a　moderate　impact　on　the　fire　resistance　of　CFSDT　columns.　Compared　with　CFSDS　specimens,　the　existence　of　the　core　concrete　significantly　increases　the　fire　resistance　of　CFSDT　columns.　The　proposed　design　model　for　fire　resistance　can　yield　a　safe　prediction.　©　2024