Acute agitation is common amongst individuals with bipolar disorder and schizophrenia and represents a medical emergency. Commonly used medications for agitation, such as benzodiazepines and antipsychotics, are often delivered intramuscularly and may cause adverse effects. Non-invasive, effective, and safe alternative treatment options are needed. The purpose of this review article is to describe the efficacy and safety of sublingual formulation of dexmedetomidine (Igalmi), a selective α2-adrenergic receptor agonist, U.S. Food and Drug Administration approved for the treatment of acute agitation in adults with schizophrenia or bipolar I and II disorder. In two phase 3 trials, two dose strengths of sublingual dexmedetomidine 180 μg and 120 μg were safe and effective in managing acute agitation in patients with bipolar disorder or schizophrenia. Both doses significantly reduced Positive and Negative Syndrome Scale-Exited Component scores two hours after receiving a single dose as compared to placebo, indicating a substantial improvement in agitation. The beneficial effects of sublingual dexmedetomidine were achieved without serious adverse events with the most common side effect being mild somnolence. The clinical trial data suggest that sublingual dexmedetomidine represents a safe and effective treatment option in the armamentarium for acute agitation for people with schizophrenia or bipolar disorder.