A method and apparatus for reassembling data blocks back into their constituent data packets in a network processor. Each data block associated with a packet is assigned a unique queue identifier for use in assembling all blocks from the same packet. The packet is also assigned a packet identifier, a start of packet identifier and an end of packet identifier for use by downstream network processors to process the packet. The blocks are assembled according to the assigned queue identifier until the last block of a packet is received, at which time the packet reassembly is complete.