The 18-year-old Hudson-Odoi was set to join the Under-21 squad in Bristol when he was told he had received his first senior call-up.
"It's been a crazy day but getting my first (senior) international call-up is an amazing feeling," Hudson-Odoi was quoted as saying by Sky Sports.
"I'm delighted to get the call... I thought the (Under-21) manager (Aidy Boothroyd) was joking. I was shocked and then when I heard that I actually had to go over, I couldn't believe it."
Ward-Prowse was also added to the squad.
"James Ward-Prowse has been called up to the England squad ahead of the UEFA EURO 2020 qualifiers against the Czech Republic and Montenegro," the FA said in a statement.
Ward-Prowse, 24, claimed one senior cap two years ago when England lost 1-0 to Germany in a friendly. He has scored six league goals for Southampton this season, including two free kicks against Manchester United and Tottenham Hotspur in his last two Premier League games.
England play Czech Republic on Friday at Wembley Stadium and face Montenegro away on March 25.
England 23-man squad
Goalkeepers: Tom Heaton, Jack Butland, Jordan Pickford
Defenders: Trent Alexander-Arnold, Ben Chilwell, Michael Keane, Harry Maguire, Danny Rose, Kieran Trippier, Kyle Walker, James Tarkowski
Midfielders: Ross Barkley, Dele Alli, Eric Dier, Jordan Henderson, Declan Rice, James Ward-Prowse
Forwards: Harry Kane, Marcus Rashford, Jadon Sancho, Raheem Sterling, Callum Wilson, Callum Hudson-Odoi
(This story corrects date of Montenegro game to March 25 in last para.)
(Reporting by Rohith Nair in Bengaluru,; Editing by Ed Osmond)
