Decapod crustaceans rely on multiple chemosensory organs such as the walking leg dactyls and lateral flagella (LF) of the antennules for chemical sensing. Chemosensory neurons in these organs rely on certain classes of receptor proteins to act as external sensors and to regulate signal transduction. G-protein coupled receptors (GPCR) regulate neuronal activity in most animals and mediate chemical sensing in many animals (primarily vertebrates). GPCRs are pervasive throughout the animal kingdom, and the class A (rhodopsin-like) sub-family is the most diverse group. Class A GPCRs regulate neurotransmission and neuromodulation, and serve as receptors for external stimuli of many modalities. To identify gene expression of GPCRs in chemosensory organs of decapod crustaceans, we analyzed transcriptomes from LF and dactyl from four decapods: Panulirus argus, Homarus americanus, Procambarus clarkii, and Callinectes sapidus. We also analyzed single cell transcriptomes (SCT) from olfactory sensory neurons (OSNs) of P. argus. Putative GPCRs were identified through InterProScan and phylogenetically classified based on sequence similarity. In total, 399 putative class A GPCR sequences were detected with 99 from P. argus, 94 from H. americanus, 125 from P. clarkii, and 81 from C. sapidus. Homologues were separated into six sub-classes comprising 13 opsins, 28 small molecule receptors, 49 neuropeptide receptors, 7 leucine-rich repeat-containing GPCRs, 18 deuterostome-like GPCRs, and 31 orphan GPCRs. Collectively, 63 sequences were enriched in the chemosensory organs, 45 had higher expression in the LF than the dactyl, and 54 sequences were expressed in OSNs of P. argus. We identified potential modulatory GPCRs such as a metabotropic histamine receptor, and several orphan receptors and opsins that may serve as environmental sensors.