Defoe's last appearance for his country came in November 2013, but he returns to the squad four years older than any of his teammates.
The Black Cats forward has acknowledged that it feels "strange" to be seen in that position, but he is keen to pass on his experience to the younger players in Gareth Southgate's squad.
The 34-year-old told reporters: "It feels different coming in as one of the senior lads. When you come in as a youngster, you're like a sponge where you try to take everything from everyone.
"This time around, it's a bit strange because you are a senior lad and you want to try to help the younger lads, but even the younger lads have got some experience under their belt, which is important."
Defoe has netted 19 goals in 55 matches for the Three Lions.