It happened outside the Westin Hotel in the 900-block of North Michigan Avenue around 8 p.m. about an hour after the Magnificent Mile Lights Festival wrapped up.
The man, identified as Dr. Mir Shah, was taken to Northwestern Memorial Hospital in serious but stable condition.
Family members said Dr. Shah had enjoyed the lights festival with his family and was having dinner at the grill in the hotel.
Shah was attacked in the bathroom.
An employee of the Westin rushed to help him and stop the man who tried to rob Shah.
The suspect was taken into custody but no charges have yet been filed.
The Shah family released a statement thanking the police department and the Westin and Northwestern Hospital.
It goes on to say quote "This was an enjoyable night out for the family (that) turned horribly tragic - but it could have been much, much worse. Dr. Shah was senselessly attacked and we were fortunate to be able to summon help."