The two-time major champion dug deep to defeat American Jessica Pegula 2-6 6-3 6-4 in their semi-final on Saturday, advancing to her biggest final since winning Rome in 2020.
World No.24 Haddad Maia of Brazil continued her breakthrough season as she beat last year's finalist Karolina Pliskova 6-4 7-6 (9-7) in just over two hours.
Halep, 30, will be seeking a third Canadian Open title, having hung on to claim her 37th victory of the year despite producing 10 double faults and putting fewer than 60 per cent of her first serves into play.
With the win, Halep will re-enter the top 10 for the first time in almost a year when the new rankings are released on Monday.
"The fire is back," said Halep when asked about moments in the match where she appeared poised to take out her frustration on her racquet.
"It's a good sign if I do that... it helps me sometimes. I don't know always if it's good or not. But it helps me."
Haddad Maia looms as a formidable challenge for Halep.
The 26-year-old beat Halep in the semi-finals of the Birmingham Classic earlier this year, a tournament she went on to win for her lone WTA title.
The Brazilian has won 17 matches on tour since June, second only to Caroline Garcia's 20 match-wins during that timeframe.
This season, Haddad Maia has made five semi-finals or better at tour-level; only Iga Swiatek (8) and Halep (7) have more semifinal-or-better showings in 2022.
The Brazilian has gone 7-1 against Top 20 players this year, with four of those wins coming this week, including Saturday's win over Pliskova.
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