This　study　experimentally　investigated　the　out　-of　-plane　flexural　behavior　of　assembled　composite　walls　(ACWs).　An　experimental　database　was　established,　and　seven　specimens　were　tested.　The　effects　of　several　parameters　were　investigated,　including　steel　plate　thickness,　distance　between　two　steel　plates,　and　external　concrete　layer　thickness.　The　results　showed　that　ACW　specimens　exhibited　promising　out　-of　-plane　flexural　strength　compared　to　the　reinforced　concrete　specimen.　The　ductility　increased　with　increasing　distance　between　two　steel　plates　and　increasing　thickness　of　the　external　concrete　layer,　while　the　effect　of　steel　plate　thickness　was　minor.　The　flexural　strength　and　stiffness　of　the　specimens　were　improved　with　increasing　values　of　the　three　test　parameters.　Experimental　results　were　used　to　evaluate　the　applicability　of　current　design　provisions　(ACI　349M-06,　GB　50936-2014,　and　JEAC-4618)　for　estimating　flexural　strength.　It　was　indicated　that　the　design　equations　of　ACI　349M-06　estimated　the　out　-of　-plane　flexural　strength　with　reasonable　accuracy.