The 21-year-old Pakistani , who is currently living in a communal refugee home in the west German town, was walking along the banks of the Rhine with a friend on Sunday when he spotted the local, police reported.
The 20-year-old Krefelder had been celebrating at the local carnival, where copious amounts of alcohol are normally consumed.
While he was relieving himself of the extra liquid he'd taken on over the past few hours, the younger man lost his footing and slipped into the huge river, which in Krefeld is around 300 metres wide.
After telling his friend to alert the emergency services, the Pakistani jumped into the water to rescue the unfortunate man.
He pulled him out and both men remained uninjured.
The Krefeld Karneval had a turnout of around 80,000 revellers on Sunday.
The day passed relatively peacefully, although one 34-year-old local was arrested for causing serious bodily harm.