Polyalthia suberosa (Roxb.) is a plant used to cure coughs, dysentery, fevers, joint aches, rheumatic pain, inflammation, and a variety of skin diseases. The aim of the study was to evaluate the ethyl acetate extract of Polyalthia suberosa (P. suberosa) leaves and their effects on mice for neuropharmacological, analgesic, and antidiarrheal activities. For neurological studies, the hole cross, hole board, open field, and thiopental sodium-induced sleep duration measurement methodologies were used. The castor oil-induced diarrhea inhibition test was used to assess antidiarrheal action, and the acetic acid-induced writhing inhibition test was used to determine analgesic effectiveness. The extract was given in doses of 250 and 500 mg kg−1 body weight. As a standard drug, diazepam at a dosage of 3 mg kg−1 was used. The extract was also given to groups, and sleep time was measured and recorded. The onset of the anxiolytic effect of the extract at both doses was found to be significant ( < 0.001), and sleep time increased to 273 minutes. For assessing analgesic activity, the extract along with standard diclofenac was administered and found to be 55.02 percent and 64.33 percent, respectively, for the extracts, and diclofenac was found to be 67.44 percent ( < 0.001). For antidiarrheal activity, it was compared with the standard drug, loperamide. The decrease for plant extracts was 50.07 percent and 70.06 percent at 250 mg kg−1 and 500 mg kg−1, respectively, whereas it was 85.01 percent for loperamide (3 mg kg−1) ( < 0.00). In this study, it was found that ethyl acetate extract of Polyalthia suberosa leaves had strong CNS depressant, analgesic, and antidiarrheal activities, which indicates that it may be used in contemporary medicine.