The Glovers keeper spilled a James Perch free kick delivered high into the box and allowed Grant Holt to lash home the only goal of the game in confident fashion.
It was the striker's 14th goal of the campaign - and it was sufficient to guide the Reds back into the automatic promotion places.
Forest never reached the heights they achieved last weekend, when they knocked Premiership Charlton out of the FA Cup. But they did enough to claim a vital three points from a stubborn Yeovil side who demonstrated why they had only been beaten five times previously this season.
There was a cagey opening to the game from both sides but, while chances were few in number, both Forest and Yeovil demonstrated themselves capable of producing some neat flowing football.
In truth, it was the visitors who looked the more likely to carve out an opening as they prodded and probed at the Forest defence with a simple, patient approach.
The makings of an intriguing battle between Leon Best and full-back Julian Bennett were developing down the Forest left - but it was Yeovil midfielder Anthony Barry who forced the first save of the match.
Best had been involved in the build up as Yeovil pressured the Forest goal and, when the ball broke to the edge of the area, Barry hit a dipping first-time volley that Paul Smith was well placed to hold, just inside the post.
At the other end Holt and Junior Agogo were struggling to find the same cohesion that they had demonstrated against Charlton last weekend and, as a result, Forest were left lacking a cutting edge.
It took until the 19th minute for them to pose a threat - but when they did they should perhaps have scored, as Nathan Tyson broke down the left and crossed menacingly into the middle, only for Holt to fail to properly connect with an eight-yard header.
This lifted Tyson's confidence however, as it became clear he had the better of the Yeovil defence for pace, as demonstrated when he broke clear once more, only to see Mildenhall make a smart stop.
The Yeovil keeper had also made another significant save, to deny Bennett as he prodded a corner goal wards. But generally Forest were lacklustre.
Veteran front-man Marcus Stewart forced a decent stop from Smith at the other end, as he fired in an angled shot on the turn. While Tyson threatened again with a 30-yard free-kick that skimmed off the turf and forced Mildenhall to dive swiftly to his right to block.
But it remained a scrappy game in which both sides found it hard to carve out much in the way of chances.
It always seemed likely that it would need a mistake to create the opening and so it proved, just two minutes into the second half. An awful gaff from Mildenhall saw him spill a Perch free kick for the second time in the match - and this time pay the price, as Holt lashed home the loose ball in confident fashion, from just inside the box.
The goal lifted Forest and they produced their first meaningful spell of pressure, with Perch unlucky to see a driven effort deflected wide.
Agogo could have no such complaints however, as he twice powered fine headed chances wide of the post, as Forest went in search of a vital second.
Although Best was also guilty of a bad miss, as he planted a header of his own wide of the target, as Yeovil spurned a fine chance of an equaliser.
Smith was forced into the save of the game, however, as substitute Ishmael Welsh almost made an immediate impact with an arrowed shot that was bound for the bottom corner until the keeper stretched to palm it away.