A differential thermal mass flow meter assembly (1) for measuring a mass flow of a gas or liquid is disclosed, wherein it comprises: a flow channel (2), in which the gas or liquid is flowing, at least two heating elements (4, 4′, 4″) arranged in the flow direction on the inside wall (3) of said flow channel (2), at least one thermal sensor (5) arranged in the flow direction up-stream said heating elements (4, 4′, 4″) on the inside wall (3) of said flow channel (2), at least one thermal sensor (6″) arranged in the flow direction down-stream said heating elements (4, 4′, 4″) on the inside wall (3) of said flow channel (2), as well as a method of measuring the mass flow of a gas or liquid using said differential thermal mass flow meter assembly.