Armstrong was claimed off waivers by the Orioles on Sunday, Roch Kubatko of MASN Sports reports.
Armstrong was designated for assignment by the Mariners on Thursday and now has a new home in Baltimore. Kubatko also noted that Armstrong is out of options so will be placed on the team's 25-man roster once he reports. Armstrong has struggled early on this season, allowing six earned runs in just 3.2 innings of work, and figures to serve as more depth in team's bullpen.