Kiernan joined the 3d staff full time in 2017. Prior to that, he coached for 3d in Houston, Memorial High School and the Memorial Knights youth program.

Before 3d Kiernan was the graduate assistant at Concordia University Wisconsin. While there for the 2014 and 2015 seasons, the Falcons broke 19 single game and season records along with hosting their first post season game and making their first appearance in the conference finals. Statistically the Falcons were in the top ten in 5 categories nationally for NCAA division III most notably leading the nation in man-up offense in 2015. While at CUW, Kiernan had a 24-11 record and coached 18 All Midwest Conference selections.

As a player Kiernan played for Claremont Sports Institute High School before heading to Mars Hill University. As a Lion, he was part of the Deep South Conference Champion all four years. After college Kiernan made an appearance with the Irish National team in 2013 helping them capture the Celtic Cup.

Kiernan played with the Peninsula Lacrosse Association growing up, where he was Player of the Year for the association in 2007. He was drafted to the Nanaimo Jr. A Timbermen but played the majority of his Junior career with the Peninsula Jr B Warriors where he was an assistant captain, 3-time All-star Selection, and MVP in 2012.

 Kiernan graduated from Mars Hill University with a bachelor’s degree with a double major in Organismal Biology and Chemistry. Kiernan received his Masters of Applied Exercise Science from Concordia University.