The Sheffield United goalkeeper was summoned to St George's Park aftter Aston Villa's Tom Heaton was forced to withdraw through injury.
Although Jordan Pickford of Everton remains in pole position to start Friday's Euro 2020 qualifier against the Czech Republic, Henderson could feature against Bulgaria on Monday. If he does appear in Sofia, the 22-year-old will become the first United player to represent the Three Lions since Brian Deane nearly three decades ago.
"This is fantastic recognition for Dean and the club as a whole," Chris Wilder, the United manager, said. "Everyone at Sheffield United will be delighted to hear this news, and we wish Dean well on international duty."
Henderson, on loan from Manchester United, was first mentioned as a future full international after helping Wilder's squad win promotion from the Championship last term.
Impressed by his performances at under-21 level, Southgate admitted Henderson was on his radar and has watched him in action several times this season.
After being criticised for his error during United's recent defeat by Liverpool, the youngster proved both his character and his calibre by producing several key saves during United's draw at Watford four days ago.
In a post on his twitter page following the announcement, Henderson wrote: “This is what dreams are made of... it’s a dream come true to receive my first @England senior call up!!”
Henderson, who becomes the sixth United player called-up by their respective countries during the international window, will travel to Prague for Friday's Group A tie before visiting Sofia on Monday.
Enda Stevens, Callum Robinson and John Egan reported for duty with the Republic of Ireland following United's trip to Vicarage Road while John Fleck and Mo Besic are working with Scotland and Bosnia and Herzegovina respectively.