This　paper　summarizes　current　literature　evidence　on　the　associations　of　indoor　carbon　dioxide　(CO2)　with　sleep　quality　and　other　human　responses　at　dorms,　bedrooms　or　other　sleeping　environments.　Published　literature　was　identified　by　searching　Web　of　Science　and　Google　Scholar,　using　the　following　keywords　including　carbon　dioxide,　sleep　quality,　ventilation　rate,　indoor　air　quality,　and　health　effect.　From　selected　studies,　detailed　findings　were　summarized　based　on　subjective　assessments　and　objective　measurements.　The　collected　data　were　then　tabulated　to　observe　the　associations　of　CO2　concentration　with　sleep　quality　and　other　human　responses.　Furthermore,　the　potential　confounding　of　researches　was　discussed.　The　results　of　the　reviewed　studies　show　that　there　was　a　tendency　that　lower　CO2　concentration　improved　sleep　quality.　Given　the　findings　of　this　summary,　effects　of　indoor　CO2　concentration　on　sleep　quality　are　worthy　for　further　study　to　elaborate　the　dose-response　relationship　between　CO2　concentration　and　human　responses　during　sleep　and　＇no-effect＇　threshold　of　CO2　concentration　for　good　sleeping　environment　requires　further　research.　©　2020,　Springer　Nature　Singapore　Pte　Ltd.