Kielczweski has boxed since the age of six, when his father, Rick, first took him to the annual South Boston St. Patrick’s Day boxing tournament in 1996.
118-26 amateur record. Won gold in 2007 and 2008 New England Golden Gloves Tournament.
He trains at Cyr-Farrell Boxing Gym, in his hometown of Quncy, MA, under trainer Jimmy Farrell Jr., and his managed by his father.
The “Polish Prince” turned pro on DiBella Entertainment’s “Broadway Boxing” series, on August 6, 2008, winning a four-round unanimous decision (all 40-36) over Raphael Luna.
Moved up to six-rounders in his seventh pro fight, then eight-rounders in his 10th pro bout.
Scored two knockouts, both in the third round, in 2009, against Aaron Chavez on March 19, and Norman Allen on Sept. 11.
On October 21, 2011, won a six-round unanimous decision over Willie Villanueva, at Foxwoods Resort and Casino, in Mashantucket, CT.
In front of his local fan base at the House of Blues, in Boston, on May 24, 2012, Kielczweski earned an eight-round unanimous decision (all 79-73) over his most experienced foe, the 24-8 Ira Terry.
On September 29, 2012, Kielczweski scored a six-round unanimous decision (60-54 twice, 59-55) over Jeremy McLaurin, back at Foxwoods.
To start 2013, Kielczweski scored his first knockout in three-and-a-half years, dropping Washington Hago twice with body shots, en route to a TKO2, on January 26 at Boston’s TD Garden.
At the MGM Grand at Foxwoods, in Mashantucket, CT, on March 1, Kielczweski earned a unanimous decision over the always-tough Gil Garcia. Following eight exciting rounds, the scorecards read 80-72 twice, and 79-73, all for Kielczweski.
Fighting in Salem, NH, at Rockingham Park, Kielczweski faced undefeated knockout artist Miguel Soto, 11-0 (11 KOs), in the opening bout of ESPN’s “Friday Night Fights” series on July 19. Celebrating his 24th birthday, Kielczweski systematically broke Soto down, jabbing and setting up his straight right hand early on. By the third frame, Kielzweski was landing his left hook, causing some swelling to Soto’s right eye. Timing Soto’s advances, Kielczweski began landing his right uppercut. In round five, as he upped his punch output, Kielczweski landed a beautiful left hook square on Soto’s chin, knocking him down face first. The bout was immediately waved off, at 2:59 of the frame.
On St. Patrick’s Day, March 17, 2014, Kielczweski fought in front of local fans at the House of Blues, in Boston, MA, winning a six-round unanimous decision over Guillermo Sanchez.