In the MLB, only one pitcher can be awarded the win. A win for a pitcher is not just the outcome of the game. A pitcher receives a win when he is the pitcher of record when his team takes the lead for good.
Rare exceptions
Starting pitchers must pitch at least five innings (in a traditional game of nine innings or longer) to qualify for the win. If he does not, the official scorer awards the win to the most effective relief pitcher.
Source: Official MLB Glossary