The invention is directed to an incubator for infants wherein air is supplied from an air supply opening arranged between the side walls of the incubator hood and the supporting member defining a supporting surface for accommodating the infant. The air flows upwardly along the side walls of the incubator hood to form an air curtain arranged in surrounding relationship to the infant. An air return channel conducts the air from the vicinity of the top wall of the incubator hood to an air return space below the supporting member. A blower moves the air through the air return channel and into the air return space from where the air can flow upwardly through the air supply opening. Because of the air curtain, there is a temperature gradient only in the vertical direction; however, in the horizontal direction, the temperature gradient is virtually zero so that all regions of the body of the infant lying on the supporting surface are warmed by air at a uniform temperature. In addition, the formation of condensate in the air return channel is prevented because the air curtain and the air return channel are completely within the space enclosed by the base of the incubator and the incubator hood mounted thereon.