Filomena Tassi, a chaplain at Bishop Tonnos Catholic Secondary School in Ancaster, found herself in the national media spotlight this week after she was asked for her views on abortion. The Hamilton Spectator reported that Tassi said she was "pro-life."
The Liberal leader announced in May that MPs elected in 2015 would be expected to vote against putting limits on abortion.
Asked how she would vote on a private member's bill that would restrict abortion, Tassi appeared to suggest she would have to see the details of the bill before making a decision, but did not rule any option out.
Trudeau, who was in Winnipeg on Friday, said all Liberal candidates have passed through a process in which they had to agree to support the party's pro-choice stance.
He characterized the party's vetting process as "very rigorous and very clear."
Trudeau dismissed the need to call for Tassi's resignation, saying "she has already agreed to vote in favour of a woman's right to choose. That's how she's become a candidate."
CBC News was unable to reach Tassi on Friday.
Trudeau, who pledged to hold open nominations, has come under scrutiny from an increasing number of Liberal members who say the party has favoured some candidates over others.
On Friday, Trudeau lauded the process of open nominations, saying it was a "reflection of democracy."
"Yes, there are competitions that have winners and people who don't do so well — but the reality is it's been an extremely positive experience for the Liberal Party of Canada."