Greenway, who will make his first Pro Bowl appearance, had a personal-best 174 tackles this season. He will replace the injured Lance Briggs of Chicago. The Vikings made the announcement Monday.
Fletcher is replacing another Bears linebacker, Brian Urlacher, who suffered a knee injury in Chicago's season finale.
Fletcher made the announcement via his Twitter page Monday.
He wrote: "Aloha! Officially added to the pro bowl roster today!"
Greenway has led the Vikings in tackles for four straight seasons. The team said he has 104 solo and 70 assisted tackles this season.
Fletcher led the NFL in tackles, forced three fumbles, and had two interceptions and 1½ sacks.
Fletcher once referred to himself as "the Susan Lucci of the NFL" because he had yet to be rewarded with a trip to the Pro Bowl. In 2010, Fletcher made it for the first time when Jonathan Vilma of the New Orleans Saints couldn't play because the game was being held before the Super Bowl.
Last season, Fletcher got in again at the last minute -- after Urlacher withdrew because of an injury.
The Pro Bowl will be played Jan. 29 in Honolulu.
Information from The Associated Press was used in this report.