The Candystripes cannot now be caught for fourth place as they cemented their grip on third spot with leaders Dundalk beating Shamrock Rovers 3-0.
Derry made a slow start as Kurtis Byrne put Bohs ahead on 17 minutes.
Aaron McEneff levelled from a 51st-minute penalty before Rory Patterson struck the winner on 64 minutes.
Derry were full value for their victory as they hit the woodwork twice before McEneff's equaliser.
McEneff hammered against the crossbar with a fierce drive on 30 minutes with Patterson seeing his shot rebound to safety a few minutes later with Bohs keeper Dean Delany again beaten after great work by Dean Jarvis and Josh Daniels.
However, Derry got on terms six minutes after the restart as McEneff netted his spot-kick following a mistimed challenge from Derek Pender on Jarvis.
Derry were in front 13 minutes later with Patterson getting the final touch following a goalmouth scramble, for his 18th goal of the season.
As Derry took total control, Delany made a great save to turn away a Ronan Curtis header although Bohs almost snatched an undeserved draw in injury-time as Derek Prendergast headed inches wide.
Derry's win moved them five points ahead of fourth-placed Shamrock Rovers with only their remaining games against Sligo Rovers and St Patrick's Athletic to come.

The Slovak showed great determination to beat Russian Svetlana Kuznetsova 1-6 7-6 (7-2) 6-4.
Kerber, the Australian Open and US Open winner, was too strong for defending champion Agnieszka Radwanska.
The German dominated for a 6-2 6-1 victory over the Pole to make it six wins apiece in their head-to-heads.
"It's just amazing to be here,'' said Kerber, who is playing in the event for the fourth time.
"It's been an incredible 12 months. I've been really working at being focused, being calm and being positive on court and this is the biggest improvement I've made."
After a disappointing first set, in which Cibulkova trailed 4-1 after being broken twice in her first three service games, the world number eight showed far more intensity in the second set.
She improved her first-serve percentage dramatically from 42% to 79% with Kuznetsova, who was in superb form in the opening set, happy to sit back and wait for any opportunities.
Cibulkova, making her first appearance at the elite eight-player event, squandered chances to secure the second set while serving at 5-4 and 6-5 but in the tie-break she recovered quickly to set up four set points and level the match.
Kuznetsova, 31, took a 10-minute break at the end of the second set to change her kit but while it initially did not appear to unsettle Cibulkova, who broke to go 2-0 up, she again was unable to take advantage of the break.
Two-time Grand Slam tournament winner Kuznetsova won the next four games to lead 4-2, only for a gutsy Cibulkova to roar back with four straight games of her own to clinch a place in the final.
Derry City guaranteed themselves a Europa League spot next summer as they came from behind to beat Bohemians in the League of Ireland Premier Division.
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Debutante Dominika Cibulkova will meet world number one Angelique Kerber in Sunday's final at the WTA Finals in Singapore.