Officers responded to a call at about 6:30 a.m. on Thursday and found the partially dressed baby in an outdoor recycling bin with life-threatening injuries, police said.
They added the little girl had been outside for several minutes before being discovered. She was transported to hospital and is now listed in stable condition.
A police spokesman said the incident started when a fight broke out at a house party.
"The accused grabbed the infant and ran off," said Const. Eric Hofley.
He said the suspect then tripped, fell on the child and "discarded her in the dumpster" before returning to the home and getting into a fight with a 13-year-old female.
"It was at the time approximately -30 C with the wind chill here in Winnipeg, and the child only had on a diaper and pants," said Hofley.
It was "just by the grace of good fortune" that a male who had been chased off from the party heard the baby crying and called police, he said.
The baby, the 13-year-old girl and the accused are related, police said without providing further details.
A 17-year-old boy faces charges including criminal negligence causing bodily harm, abandoning a child, possession or consumption of liquor by a minor and assault.