The 30-year-old was diagnosed with ulcerative colitis in 2011 and has seen his career disrupted by the illness but the midfielder returned to action earlier this season
Manchester United midfielder Fletcher has missed most of the last 18 months due to a chronic bowel condition called ulcerative colitis that forced him to have surgery.
The 30-year-old was originally diagnosed in 2011 and made his last Scotland appearance in the 2-0 defeat against Belgium.
Fletcher sat out the majority of last season, but Fletcher returned for United in December and has done enough to earn a recall.
With 61 caps to his name, Fletcher's availability has been welcomed by head coach Gordon Strachan.
He told reporters: "It was wonderful over the Christmas period to see him back playing football.
"We have got to take it a stage further. I've seen him playing and he has lost none of his enthusiasm, which he will never lose.
"To have him back in the squad is terrific."
The midweek friendly at Stadion Narodowy in Warsaw will serve as vital preparation for both sides ahead of their qualification campaigns for Euro 2016.
Scotland and Poland found themselves drawn alongside each other in Group D with Germany, Republic of Ireland, Georgia and Gibraltar.
Poland are in decent form having lost three of their last 12 in all competitions, but two of those defeats came in their final World Cup 2014 qualifiers, ending their hopes of reaching Brazil.
Scotland, meanwhile, have responded to a run of six defeats in nine matches by winning three of their last four, including victories over Norway and Croatia.
Poland coach Adam Nawalka is without a few regulars as the injured Jakub Blaszczykowski is joined by Jakub Wawrzyniak, Adrian Mierzejewski, Adam Matuszczyk and Pawel Brozek in missing out.
Leigh Griffiths has been handed a recall to the Scotland squad and celebrated in style at the weekend, netting a hat-trick for Celtic, while 19-year-old defender Andrew Robertson could make his debut in place of the injured Grant Hanley.