Both players were on Monday rewarded for stirring performances in the Caribbean Premier League (CPL) and were the only new faces in the squad which will once again be led by emerging all-rounder Carlos Brathwaite, reports CMC.
However, marquee opener Chris Gayle will not feature after advising the Courtney Browne-led selection panel of his unavailability.
The veteran left-hander was included for the hastily arranged two-match series against India last month in Florida, but never played due to injury.
Opener Lendl Simmons has also been left out because of "medical reasons", the West Indies Cricket Board said.
However, the bulk of the squad remains unchanged, with the likes of star all-rounders Andre Russell, Kieron Pollard and Dwayne Bravo, along with off-spinner Sunil Narine, all named in the line-up for the three-game series from September 23-27 in Dubai.
Pooran and Powell, however, were two of the standouts from the CPL, shining with the bat for their respective franchises.
Test players Kraigg Brathwaite and Alzarri Joseph are set to make their One-Day International debuts after being named in the Jason Holder-led 15-man squad.
The three-match One-Day series runs from September 30 to October 5, with the first two matches in Sharjah and the last one set for Abu Dhabi.
A three-Test series follows the limited overs tour and will run from October 13 to November 3.
The squads: T20 : Carlos Brathwaite (captain), Samuel Badree, Dwayne Bravo, Johnson Charles, Andre Fletcher, Jason Holder, Evin Lewis, Sunil Narine, Kieron Pollard, Nicholas Pooran, Rovman Powell, Andre Russell, Marlon Samuels, Jerome Taylor, Chadwick Walton.
ODI : Jason Holder (captain), Sulieman Benn, Carlos Brathwaite, Kraigg Brathwaite, Darren Bravo, Jonathan Carter, Johnson Charles, Shannon Gabriel, Alzarri Joseph, Evin Lewis, Sunil Narine, Ashley Nurse, Keiron Pollard, Denesh Ramdin, Marlon Samuels.
