Ribosomal protein S23 (RPS23) constitutes the ribosomal binding site for mRNA in the 40S initiation complex, and appears to be involved in initiating the translation of messenger RNA into protein (translation step). In this study, a full-length of RPS23 cDNA was cloned from the American cockroach, Periplaneta americana (L.) (Blattodea: Blattidae) by using rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of the P. americana RPS23 (PaRPS23) was of 615 bp, containing a 5′ untranslated region (UTR) of 116 bp, a 3′ UTR of 67 bp with a poly (A) tail, and an open reading frame of 432 bp encoding a polypeptide of 143 amino acids with the predicted molecular weight of 16.03 kDa and estimated isoelectric point of 10.47 (NCBI accession number: KJ472479). BLAST analysis revealed that amino acids of PaRPS23 shared identity with Graphocephala atropunctata (Signoret) 99%, (Hemiptera: Cicadellidae), Tribolium castaneum (Herbst) 99%, (Coleoptera: Tenebrionidae), Pediculus humanus corporis L. 98%, (Phthiraptera: Pediculidae), Riptortus pedestris (F.) 98%, (Hemiptera: Alydidae), Biphyllus lunatus (F.) 98%, (Coleoptera: Biphyllidae), Maconellicoccus hirsutus (Green) 97%, (Hemiptera: Pseudococcidae), and Drosophila yakuba Burla 97%, (Diptera: Drosophilidae) and so on. Quantitative RT-PCR analysis indicated that PaRPS23 could be detected in all the tested tissues, in which the relative expression levels were 1.2-, 17.9-, 7.3-, 5.6- and 2.2-fold higher in the ovary, head, thorax, leg and gut than in the testis, respectively. The results provided some important base data for further functional studies in P. americana, and the information may also help to understand the evolution of ribosomes in insects.