In 2011, Niagara United were elevated to the professional ranks by joining the Canadian Soccer League, and competed in the CSL Second Division.

[6][7] Niagara United hosted a friendly match against Bedlington Terriers FC, then playing in the English Northern Football League, on June 28, 2011, losing 4-1.

[11][12][13] Kalar Sports Park the team's home ground received several grants in order to accommodate the facility for CSL standards.

[14][15][16] Niagara made their professional debut on May 26, 2012 in a sellout crowd against Brantford Galaxy in a 2-1 defeat with Derek Paterson scoring the lone goal.

[22] For the 2013 season McGillivary re-signed the majority of his players with notable additions as Liberian international Preston Corporal, Keith Makubuya, and Gary Boughton.

[25] The season was marked with injuries, shortage of talent, and a lack of player commitment which resulted once more in a last place finish in the overall standings.