A vehicle heater includes a burner area, a circumferential wall providing a combustion chamber, a flame tube with a first end forming or adjacent to a part of the combustion chamber circumferential wall and a second flame tube end. A heat exchanger housing has a circumferential wall enclosing the flame tube. A waste gas backflow space is formed, between an outer side of the flame tube and an inner side of the heat exchanger housing circumferential wall, with an inlet area at the second flame tube end and with an outlet area in the area of the first flame tube end. An inner dimension of the circumferential wall increases in the direction from an inlet area of the waste gas backflow space to an outlet area. An outer dimension of the flame tube increases in the direction from the second flame tube end to the first flame tube end.