FMRFamide-like peptides (FaLPs) are neuropeptides that play a pivotal role in regulating various physiological processes in insects and other arthropods including behaviour, reproduction, and homeostasis. FaLPs mostly act through G-protein coupled receptor and influence muscle activity by modulating Ca influx. Historically, the function described for these neuropeptides was primarily associated with myostimulatory activity. After more than three decades of research, it is now well established that FaLPs are implicated in the regulation of circadian rhythms, affecting locomotor activity and phase changes in response to environmental cues. During reproduction, FaLPs influence contractile activity in both the male and female reproductive systems. They also participate in physiological processes such as diapause induction, sleep modulation, and flight regulation in insects. Similarly, in crustaceans, FaLPs regulate the circulatory system, stomatogastric nervous system, and muscle contractions. Nowadays, it is also known how the physiological properties of FaLPs in arthropods share similarities with mammalian RFamide peptides, which are involved in a wide range of functions, including muscle contraction, feeding, reproduction, and stress responses, mediated through various RFamide receptors. Therefore, summarizing the investigated physiological functions in arthropods may be relevant also for future research aiming to test their activity in other organisms such as mammalians.