Chitin, a polymer of β-1,4 N-acetyl-glucosamine (GlcNAc), is metabolized by chitinases, enzymes that modify chitin matrices. These enzymes offer insights into arthropod development, with implications for agriculture, ecology, and health. This study used arthropod genomes from the NCBI database to identify and characterize GH18 family chitinases. Protein sequences of primary transcripts were analyzed using Hidden Markov models. Sequences with at least one GH18 domain were selected for characterization of physicochemical properties, subcellular localization prediction, phylogenetic inference, and Hierarchical Orthologous Group (HOG) analysis. Conserved motifs were also examined. Data from 231 species across Chelicerata, Crustacea, and Hexapoda were analyzed, with a predominance of Hexapoda genomes, especially from Insecta. A total of 4,209 protein sequences with GH18 domains were identified and grouped into 75 orthogroups, 32 of which contained at least four sequences. Chelicerata and Crustacea lacked orthologs for Group V (Imaginal Disc Growth Factors) and exhibited distinct patterns in other groups. Orthogroups OG0000000 to OG0000003 were associated with known domain architectures. Other orthogroups displayed distinct architectures, highlighting the diversity and continuous evolution of chitinases in arthropods. These results underscore the diversity, specificity, and versatility of GH18 family chitinases in arthropods.