Sweden-born Johansson had been hoping to lift her first title in the country of her birth, but despite a bright start, she fell 0-6, 6-4, 7-5 to 21-year-old Hercog, ranked three places below her at world number 86.
“It was not the greatest match in general I tried to activate my self and not give up. Sometimes first set doesn’t mean anything and that was showed today” Hercog said after the match.
Hercog overcame early nerves to win the first four games of the second set and held on for a second career title after winning on her debut here last year.
Johansson lacked consistency, twice losing games where she lead 0-40 in the second and third sets, and gifted Hercog a 4-1 lead in the final set by double-faulting.
The French player fought back to make it 5-5 but then immediately dropped her serve, and the accumulation of unforced errors was ultimately to cost her a maiden title.
Johansson accumulated some 16 double faults during the match and had a first serve ratio of only 57 percent, going some way to explaining why she was unable to overcome the powerful Slovenian.