A drain support pan assembly has a drain body support pan which has a rectangular-shaped body connected to a rectangular-shaped drain receptacle body for use in floor drains. The distance between the support pan and receptacle body can be adjusted according to the depth of the floor space by selecting a predetermined length for the fasteners. The support pan has a center passageway for receiving a drain pipe and several slots that align with threaded passageways in the receptacle body for receiving the fasteners. The support pan contains concentric knock-out sections which can be removed for enlarging the diameter of the center passageway to accommodate varying diameter drain pipes or pipe connections for particular use in a deep floor space, and also has a rectangular knock-out section which can be removed for receiving the rectangular-shaped drain receptacle for use in a narrow floor space.