Kapinos signed as an undrafted free agent with the New York Jets following the 2007 NFL draft on July 2 but was released during the preseason on August 2. On November 27, Kapinos was re-signed to the Jets' practice squad. He was promoted to the active roster on December 22 when wide receiverLaveranues Coles was placed on injured reserve. He saw his first regular season action that week against the Titans, punting five times for 208 yards, including two punts inside the 20. Kapinos was then placed on the inactive list for the last game of the season. After a well-publicized 2008 offseason competition with Ben Graham, the Jets released him on June 10, 2008.
Green Bay Packers
Kapinos signed a two-year deal with the Green Bay Packers on December 3, 2008 to replace released punter Derrick Frost. He averaged 34.5 yards on 8 punts, with 3 inside the 20, in the Packers' week 14 loss to Houston. Kapinos won the preseason competition with Durant Brooks to become the Packers' regular season punter for the 2009 NFL season after leading the NFL in preseason in net punting yardage. Kapinos was also pressed into service Week 17 as the Packers' holder following a string of bad kicks by placekickerMason Crosby in previous games. According to the Green Bay Packers website, Kapinos did not receive a qualifying offer to retain his position as their starting punter for the 2010 NFL season. In late September 2010, the Carolina Panthers brought Kapinos in to mimic the left-footed punters they would face in the coming weeks: Tampa Bay'sChris Bryan, Cincinnati'sKevin Huber, and Arizona's Ben Graham.
Indianapolis Colts
On October 25, 2010, the Indianapolis Colts signed Kapinos to replace the team's regular punter, Pat McAfee, who was serving a one-game suspension for his October 20 arrest for public intoxication. Kapinos was waived on November 3 after McAfee was reinstated.
Pittsburgh Steelers
On December 7, 2010, he was signed by the Steelers to replace the injured Daniel Sepulveda, who tore the ACL in his non-kicking leg. Kapinos was going to wear the number 3, which had been worn earlier in the season by longtime kicker Jeff Reed prior to his release, but eventually decided to wear number 13 instead, being the first Steeler to don that number since quarterback Bill Mackrides wore it last in 1954. Kapinos punted in Super Bowl XLV as a Steeler, setting a Super Bowl record for average punting yardage. The Steelers lost the Super Bowl to the Green Bay Packers by a score of 31–25. He was released at the end of the 2011 preseason after a position battle with a once-again healthy Sepulveda. Kapinos re-joined the Steelers prior to Week 9 of the 2011 NFL season after Sepulveda was placed on injured reserve for the season. The team signed him to a one-year contract that offseason, offering Kapinos an exclusive rights free agent tender on February 22, 2012. He signed the tender on April 16, 2012. Kapinos was waived/injured during final cuts on August 31, 2012 after being unable to punt due to an injury.
Free agency
Kapinos was a one-week practice squad addition for the Steelers as they prepared for fellow left-footed punter Sepulveda.