Capaldi, who joined Plymouth Argyle at the end of last season having failed to make the breakthrough into the Blues first team, was selected for the first time for the Northern Ireland squad to play Estonia next wednesday.
"I'm delighted. I was a bit surprised when I heard the news, but I'm glad he (Lawrie Sanchez) as taken notice of me," Capaldi, who is now playing left midfield for The Pilgrims, told the Argyle official website.
"I don't think I would have been in this position if I'd still been in Birmingham City's Reserves."
Capaldi joined The Pilgrims as a free agent last May having been told by Blues that his contract would not be renewed when it ran out last summer.
The 22-year-old, who was actually born in Norway, has made 24 appearances for The Pilgrims so far this season and scored 7 goals.
Northern Ireland Squad. Taylor (Birmingham), Carroll (Man Utd), Murdock (Hibs), Craigan (Motherwell), Williams (Wimbledon), Clyde (Wolves), Baird (Watford), Capaldi (Plymouth), Jones (Crewe), Whitley (Sunderland), Mulryne (Norwich), Sonner (Nottm Forest), Doherty (Bristol City), Healy (Preston), Smith (Glentoran), Hamilton (Portadown), McVeigh (Norwich), Kirk (Hearts).