Geiger started working amateur, semi-professional and professional matches throughout New Jersey in 1997 and continued to do so until 2003. He later began officiating games in Major League Soccer (MLS) in 2004 and finished his MLS career with 186 regular season matches. He was named the MLS Referee of the Year in 2011 and 2014, and he was the fourth official for the 2008 MLS Cup and the referee of the 2014 MLS Cup. His final MLS match was on November 29, 2018, when he was the referee of the Western Conference Final between Sporting Kansas City and the Portland Timbers.
Internationally, Geiger has officiated in several Concacaf and FIFA competitions. In 2011, he was selected to the FIFA U20 World Cup in Colombia, where he was the referee for the final between Brazil and Portugal. He was then selected for the 2012 Olympic Games in London and the 2013 FIFA Club World Cup in Morocco. From 2016-2018, he was a Video Assistant Referee (VAR) at the FIFA Club World Cup and was appointed to the final in both 2017 and 2018. In 2017, he was chosen for the FIFA Confederations Cup in Russia.
The highlights of his career came in 2014 and 2018 when he was selected for the FIFA World Cup in Brazil and Russia. In each of those tournaments, he was the referee of two group stage matches and a Round of 16 match. In 2018, he also featured as a VAR in eight games, including the third place match between Belgium and England. For Concacaf, he has officiated in the Concacaf Champions League, including the 2017 Final between Tigres and Pachuca of Mexico. He also took part in the 2013, 2015 and 2017 Concacaf Gold Cups. Currently, Geiger is the Director of Senior Match Officials with the Professional Referee Organization (PRO), overseeing the match officials in MLS. He is also a FIFA Technical Referee and VAR Instructor.
Geiger was a VAR Instructor at the 2019 FIFA Women’s World Cup in France and a Technical Referee Instructor at the 2021 Concacaf Gold Cup. He has most recently taken part in the Women’s World Cup Referee Candidate Course and the World Cup Referee Candidate Course in Doha, Qatar, preparing referees and VARs for the 2022 World Cup in Qatar and the 2023 Women’s World Cup in Australia/New Zealand.