The Argentinian recorded a 6-3 6-3 win on the clay in Bastad, with five breaks helping him topple the top seed in their quarter-final meeting.
Ferrer, winner of the ATP 250 event in 2007 and 2012, struggled on serve throughout the match and world number 41 Berlocq took full advantage.
He also won 80 per cent of points on his first serve, meaning Ferrer's two breaks ultimately meant little.
Berlocq beat Spaniard Fernando Verdasco in last year's final and a repeat clash could be on the cards after the latter also won through to the semi-finals.
Third seed Verdasco was too good for compatriot Pablo Carreno Busta in a 7-5 6-3 win that took 88 minutes to compile.
One break in each set was enough for Verdasco, who gave his opponent little room for error with an impressive match on serve.
Berlocq's last-four match will be against Portugal's Joao Sousa, who beat Serbian Dusan Lajovic 6-4 6-4.
And Verdasco will play Uruguayan Pablo Cuevas, who reached the last four at an ATP event for the first time in more than three years.
The world number 111 saved all five of the break points he offered qualifier Renzo Olivo en route to a 6-2 6-4 triumph.