Cleveland called up Allen from Triple-A Columbus before the start of a four-game series against the Baltimore Orioles on Friday. Left-hander Scott Barnes was optioned to Columbus.
Allen quickly went through the Indians' farm system since being a 23rd-round draft pick a year ago from High Point University in North Carolina.
At three levels this year, he went a combined 3-2 with three saves and a 1.87 ERA in 31 relief appearances, striking out 53 in 43 1-3 innings.
In two years as a pro, he has a 1.74 ERA and 128 strikeouts in 98 innings.