A fuel cell assembly (1) for mounting in a vehicle comprises a fuel cell stack (2) comprising two stack units (2a, 2b) arranged in parallel. Each of the stack units (2a, 2b) comprises a number of fuel cells stacked in a fixed direction. The fuel cell stack (2) is housed in a case (3). The case (3) is supported in the vehicle via a rubber mount (36). The case (3) permits expansion and contraction of the fuel cell stack (2) in the fixed direction so that the expansion and contraction of the fuel cell stack (2) does not exert a force on the rubber mount (36).