An improved air return bulkhead for mounting on the wall of a refrigeration vehicle that carried a refrigeration unit, comprising a synthetic plastic unitary body including a generally rectangular vertical first wall having top, bottom and side edges to which are connected top, bottom and side walls that cooperate with the internal surface of the vehicle wall to define a plenum chamber. Air is drawn into the plenum chamber via apertures contained in the bottom wall for communication with the inlet of the refrigeration unit. The bottom wall of the air return bulkhead is arranged at an obtuse internal angle relative to the first wall, at least one support being provided on the interior surface of the bottom wall in downwardly spaced relation relative to the bottom edge of the first wall, the support being arranged to engage the interior surface of the vehicle wall, thereby to support the bottom wall of the air return bulkhead. Preferably, the bottom wall contains a plurality of apertures each having a rectangular configuration, the apertures being arranged in two horizontal rows with the apertures of one row being staggered relative to the apertures of the other row. According to the preferred embodiment of the invention, a plurality of supports may be provided in horizontally space relation on the bottom wall, each of the supports being in the form of a recess contained in the external face of the bottom wall. Each of the support recesses includes a vertical bottom wall arranged for face-to-face supported engagement with the vehicle wall.