Abstract: A mass flow controller assembly includes a housing defining a cavity, a plurality of internal passages, a first inlet, a first outlet, a second inlet, and a second outlet. A valve is connected to the housing, has an inlet fluidly coupled to the second outlet of the housing and an outlet fluidly coupled to the second inlet of the housing. The valve is configured to control fluid flow from the second outlet of the housing to the second inlet of the housing. A microelectromechanical (MEMS) Coriolis flow sensor is arranged in the cavity, includes an inlet fluidly coupled by at least one of the plurality of internal passages to the first inlet of the housing and is configured to measure at least one of a mass flow rate and density of fluid flowing through the MEMS Coriolis flow sensor. An outlet of the MEMS Coriolis flow sensor is fluidly coupled by at least one of the plurality of internal passages to the second outlet of the housing.