Niko Sigur

Sigur played one year of university soccer at York University in 2021. During his university career, he started in 10 of 11 matches, scoring two goals and registering one assist. He was named York's athlete of the week in November for his semifinal play-off performance, which saw him score the winning goal against Ryerson in the 119th minute and recording an assist in the same game. York would later finish with a silver medal the OUA championship during his only season.

Academy

Sigur played for Vaughan Azzurri's "C" team in 2021, making two appearances for the club in the League1 Ontario Reserve Division. Sigur moved to Slovenia in early 2022, joining Radomlje youth team.

Hajduk Split

In 2022, Sigur transferred to Hajduk Split in Croatia to play for their academy, registering two goals and three assists in his first youth season. He was ineligible to play in Hajduk Split's historic UEFA Youth League run due to a special rule where older players in the junior ages must have at least two years of club experience in order to be eligible to play. Due to injuries of Dino Mikanović and Gergő Lovrencsics, Sigur made his official senior debut as a right back in a 2–0 victory against Varaždin on April 22, 2023. He scored his first goal for Hajduk Split against Varaždin on February 24, 2024.

Toulouse

On September 1, 2026, Sigur joined Ligue 1 club Toulouse, becoming the second Canadian player in the club's history. The transfer fee was reportedly $6.5 million.

Sigur holds dual citizenship of Canada and Croatia. In 2023, he received call-ups to the Croatia U21 ahead of the 2023 UEFA European Under-21 Championship and the Canadian national team, and opted to represent the former. In May 2024, Sigur was named as a standby player for the Croatia senior national team ahead of UEFA Euro 2024. In August 2024, the Croatian Football Federation announced that Sigur had decided to switch his international allegiance and would be representing Canada. On August 27, he was officially called up by Canada for two friendly matches against the United States and Mexico. Sigur made his debut in a goalless friendly draw against the latter opponent on September 10. In June 2025, Sigur was named to the squad for the 2025 CONCACAF Gold Cup. On June 17 in Canada's opening game against Honduras, he would score his first international goal in a 6-0 victory at BC Place. He was named to the Gold Cup Group Stage Best XI after scoring his first goal and recording an assist during the group stage. In May 2026, Sigur was selected for Canada's squad for the 2026 FIFA World Cup.

Sigur was born in Burnaby, British Columbia, and first began playing soccer with Mountain United FC in Burnaby, in which he won the 2016 BC provincial championship and the 2018 BCSPL League Cup title. He was then selected to play for the Whitecaps FC Academy, winning the USSDA Northwest Division championship in 2018. He attended at Notre Dame Regional Secondary School at the high school level, where he won the 2019 BC AA provincial championship.