Abstract: A portable pet bed apparatus is provided that can be selectively side mountable to a bed assembly. The pet bed apparatus includes a carrier device that defines a bedding space thereof sized and dimensioned to accommodate a domestic pet therein. The pet bed apparatus further includes a mounting assembly having a support platform configured to vertically support the of the carrier device thereatop, and a frame assembly coupled to the support platform. The frame assembly can be moved between a stowed position and a deployed position. In the deployed position, portions of the frame assembly cooperate with the bed assembly for side mounting thereto. The carrier device can be removed from the mounting assembly, which enable independent functionality as a pet carrier.