Simona Halep (30) overcame some shaky serving to beat American Jessica Pegula (28) 2-6 6-3 6-4 and reach the Canadian Open final in Toronto, where she will face Beatriz Haddad Maia (26) for the title on Sunday.
Pegula put pressure on Halep's serve at the outset of the match and wrapped up the 35-minute first set with an ace.
But a loose service game early in the second set, capped by an unforced backhand error, gave the two-time Grand Slam champion a 3-1 lead as frustration began to mount in her less experienced opponent.
Halep broke at love for a 3-2 lead in the third set and hung on to claim her 37th victory of the year despite producing 10 double faults and putting less than 60% of her first serves into play.
The Romanian is set to face Haddad Maia, who defeated Karolina Pliskova 6-4 7-6, in Sunday's final.
