The 28-year-old has historically struggled on clay but has enjoyed a superb swing on the surface in 2019, having reached the final in Rabat a fortnight ago, where she lost in three sets to Maria Sakkari.
Bertens, a clay specialist, had been the heavy favourite to see off the Brit and took a tight opening set 5-7, but Konta struck back, claiming the second 7-5 to force a decider, which she won 6-2 to record her first top-five win since her run to the Wimbledon semi-finals in 2017.
Konta made hard work of the clash, failing to serve out the first set as Bertens surged into the lead, but broke back in the second before sailing through the third until she stood 5-2, 40-0 up before eventually closing it out on her fourth set point.
Konta has enjoyed a superb run in the Italian capital, defeating Sloane Stephens and Venus Williams within hours of each other on Thursday after Wednesday's action was rained off.
By contrast, Bertens would have gone into the clash the better rested, having received a walkover into the semi-finals after Naomi Osaka was forced to withdraw from the tournament due to injury.
Konta could potentially avenge her loss to Sakkari in the final, with the Greek set to face Karolina Pliskova in the second semi-final, later on Saturday. Should she claim the title, it will be her first trophy since winning the 2017 Miami Open.