Witnesses alerted police on Monday night that a woman was standing on Mälarbron bridge in Södertälje and looked set to jump. Officers arrived just moments after the woman took the plunge into the icy waters below.
One of the policemen didn't hesitate to jump in to try to save the woman, reported the local Länstidningen newspaper.
He then swam to the other side of the canal until he reached the woman, and brought her to the shoreline where his colleagues helped pull her to safety.
She was taken to hospital and is now in a stable condition.
Kjell Karlsson, commanding officer at the Södertälje police, said that the heroic officer had acted above and beyond the call of duty.
"It's not just anyone who can manage to swim in cold water," he told the paper.
"It's really risky. This was truly a job well done ."