Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen known to cause enterocolitis in children, amongst other types of infections. Pseudomonas aeruginosa has been widely reported as a cause of antibiotic-associated diarrhea in adult immunocompromised hosts. We present an 81-year-old previously healthy female as the first reported case of Pseudomonas aeruginosa antibiotic-associated diarrhea in an immunocompetent host in the United States.