The Orioles selected Vespi's contract from Triple-A Norfolk on Tuesday.
The 26-year-old lefty earned his first call-up to the big leagues after excelling as Norfolk's closer this season to the tune of a spotless ERA, 0.63 WHIP and .128 batting average against while converting all four of his save chances. Logan Allen was designated for assignment to clear space on the 40-man roster and 26-man active roster for Vespi, who is expected to work in lower-leverage spots in his initial opportunities with the Orioles.