Lukasz Piszczek opened the scoring in the 34th minutes for the Bundesliga side but Edgars Gauracs levelled matters three minutes after the break.
It is a disappointing result for Hertha who have lost their past four Bundesliga encounters.
There was further misery for the Germans as goalkeeper Jaroslav Drobny was forced off in the 20th minute because of injury.
Hertha were expected to comfortably see off Ventspils but the Latvians almost took a shock fifth-minute lead as Drobny did well to parry Jurijs Zigajevs' close-range effort.
And the visitors had another good opportunity moments later but Aleksejs Visnjakovs fired wide.
Hertha started to get into the game and could have taken the lead in the 16th minute when Gustavo Ramos saw his effort float wide of the left post before Piszczek sent an attempt over the bar.
Piszczek went closer shortly afterwards but Pavel Chasnowski pulled off a decent save to keep the score goalless.
Chasnowski could do nothing in the 34th minute when Piszczek lashed the ball into the bottom right corner from the centre of the penalty area.
Jevgenijs Kosmacovs should have levelled matters in stoppage time but he fired woefully wide of the left upright from six yards.
However, Ventspils' hard work paid off three minutes after the break when Igor Tsigirlash picked out Gauracs who slotted home from 12 yards.
Hertha almost instantly restored their advantage in stunning fashion with a 30-yard free-kick from Cicero which Chasnowski did brilliantly to tip round his post.
And Hertha striker Valeri Domovchiyski will be left hanging his head in embarrassment after somehow managing to head over the bar from inside the six-yard box.
Ventspils were certainly not living up to their tag of European minnows and could have gone in front as first Visnjakovs fired over the bar from the edge of the area before Grigori Chirkin saw his effort saved by Sasha Burchert.
Hertha fought hard for the winner but never looked close to scoring and Ventspils will be delighted to travel back to Latvia with a point.