Pregabalin, as the active ingredient of various medications, is used in humans to treat generalized anxiety disorder (GAD), epilepsy, fibromyalgia, and neuropathic pain. In animals, pregabalin is used as an anesthetic. The aim of the present study was to test the effect of pregabalin on the developmental parameters of Sarcophaga argyrostoma (Robineau-Desvoidy, 1830) (Diptera: Sarcophagidae), a fly used in forensic entomology. A culture of S. argyrostoma larvae was conducted on mouse carcasses. Two doses of the active substance were used in the experiment: 100 mg/kg (dose 1) and 300 mg/kg (dose 2). A control sample (without the drug) was used for comparison. The duration of the life cycle, the body weight of individual developmental stages (larvae, pupae, and adults), and their mortality were studied. The study showed that (1) pregabalin prolonged the life cycle of S. argyrostoma—dose 1 by two days and dose 2 by three days; (2) pregabalin caused an increase in body weight at each stage of development (larvae, pupae, and adults); (3) pregabalin caused high mortality among pupae. The highest mortality was observed in the treatment with 300 mg/kg. The preliminary results indicate that estimation of the time of death based on analysis of the developmental stages of S. argyrostoma on a carcass with a high content of pregabalin may be distorted relative to a case without the impact of this exogenous substance. Research on the effect of pregabalin on flies used in forensic entomology should be expanded to investigate how this compound affects the life cycles of these insects.