Sequence analysis of 168 cDNA clones encoding 12 nicotinic acetylcholine receptor subunits, Tcasα1–Tcasα11 and Tcasβ1, from the red flour beetle, Tribolium castaneum, revealed extensive post-transcriptional modification and multiple alleles. The greatest diversity was found for Tcasa6, where 18 unique transcripts, as a result of alternative and optional exon usage, were seen. A novel alternative exon 8d was found in one Tcasα6 transcript. Tcasα5 transcripts did not contain previously reported exons 8–10. Six subunits had transcripts that contained unspliced introns, which introduced premature stop codons. Intron 3′ splice site variants were seen at six intron boundaries across five subunits. A-to-I RNA editing was seen only in Tcasα6. Alleles were found for all subunit genes, except Tcasα1 and Tcasα10. Transcriptional and allelic diversity are discussed with respect to receptor function and potential interactions with insecticides.