Konta, who turned 28 on Friday, recovered after losing the last three games of the opening set to continue her impressive clay-court form.
The unseeded Brit came through after two hours and 47 minutes against the Dutch world number four, who had won the Madrid title last week.
— LTA (@the_LTA) May 18, 2019
Konta lost her first final in almost a year in Morocco two weeks ago, but will get the chance to claim the WTA Tour title when she faces Czech Karolina Pliskova on Sunday.
In defeating Bertens, the tournament’s seventh seed, it was a first victory for Konta over a player ranked in the top five since beating Simona Halep at Wimbledon in 2017.
Although Konta had responded after going 3-1 down in the first set to level at 4-4 and then lead, the Briton’s serve let her down again as Bertens edged ahead before taking her first set-point chance.
Konta levelled the match following another close second set, securing a crucial break in the 11th game and then holding serve.
She continued her momentum into the decider, pushing 5-2 ahead before needing four match points to eventually secure a spot in the final with a big serve.