A pet carrier having a removable bottom allows a shell to be placed over the pet from above, after which the bottom is slid beneath the shell and secured thereto. The shell can comprise a flexible cover such as a canvas cover removably attached to a stiff frame. In embodiments, the cover can be removed from the frame for washing and storage, and/or the frame can be folded and/or disassembled for storage. The bottom can be secured to the shell by hook-and loop attachment of folded straps inserted through loops fixed to the bottom, or the shell can be attached by pegs or quarter-turn studs that are tethered to the shell and inserted through holes provided in a lower rim of the shell and in the bottom. Mesh ventilation openings and/or a removable front panel attached by a zipper can also be provided.