Police are investigating the crime scene under the I-229 bridge near the Edmond Street exit in downtown St. Joseph.
Police say the suspect, a 48-year-old man, stabbed two other men with an unknown object.
Police say both victims and the suspect are homeless. Commander Janice Rothganger said all three men appeared to be intoxicated.
The victims, a 39-year-old male and a 46-year-old man, were both stabbed in the torso and underwent surgery at Heartland Hospital last night.
Police arrested the suspect at the scene. He remains in police custody, awaiting charges. Rothganger said the suspect was treated at Heartland for facial injuries, then released.
No names have been released.