All three players have represented the Republic at Under-21 level but this is the first time they have been named in the senior set-up.
Defender Keogh, midfielder Hendrick and striker Sammon are included in Giovanni Trapattoni's squad for the friendly against Poland at the Aviva Stadium in Dublin on Wednesday, February 6.
Trapattoni said: "I have decided to use this friendly game as an opportunity to work with younger players to see their potential.
"As a result, I have given senior players like Robbie Keane and Stephen Kelly a break for this fixture.
"We saw a number of strong performances from our younger players in the second half of last year and we intend to build from those strong foundations, using this friendly match to introduce more new talent like (Norwich forward Anthony) Pilkington, Hendrick, Sammon and Keogh.
"I look forward to working with these players and seeing what they have to offer."