Nottingham Forest scored a penalty in each half to take a giant stride towards the League One play-off final.
Commons calmly puts Forest ahead from the spot
Kris Commons put Forest ahead, calmly slotting home from the spot after Nathan Jones felled James Perch.
Perch made it 2-0 late on, striking his spot-kick into the corner after Jack Lester was upended by Terrell Forbes.
Yeovil created the better chances but Forest keeper Paul Smith was in fine form and Marcus Stewart headed wastefully against the post late on.
The Glovers will rue that missed Stewart chance, particularly as they were on top for large parts of the game.
Forest won both league meetings between the sides but without injured top-scorer Grant Holt, the man who scored the only goal in both games, they struggled to retain possession and looked second-best in the opening 20 minutes.
The pace of Aaron Davies and Wayne Gray and the knowhow and trickery of Stewart and Lee Morris troubled the visitors early on.
Keeper Smith was forced to make a stunning stop low to his right to keep out Davies' fierce strike and Stewart also tested the Forest number one.
Forest had to wait until 21 minutes for their first chance, the impressive Lewis McGugan blazing a shot over the bar from the edge of the box after some neat footwork.
But within seconds they were ahead.
Commons played a teasing through-ball into the penalty area and Jones tried to nip the ball away from the on-rushing Perch but only succeeded in sending the Forest man tumbling.
Commons took the responsibility from the spot, calmly stroking the ball into the bottom corner.
Forest were enjoying their best spell of the match and only a superb last-ditch blocked tackle by Forbes prevented Commons from doubling the lead.
But the Glovers continued to create half-chances.
Chris Cohen shot tamely at Smith before the break and two minutes after the restart the impressive Davies beat three men but delayed his shot too long, giving Ian Breckin enough time to get in a vital block.
Forbes then sent a header inches wide after a fine Stewart cross and Stewart headed a difficult chance wide while Gray was also denied by another superb diving stop from Smith.
At the other end Commons saw a well-struck half-volley deflected over and Scott Dobie sent a shot narrowly wide after a positive run from the half-way line.
With 18 minutes left Stewart squandered Yeovil's best chance of the game, heading Anthony Barry's cross against the post from point-blank range.
And with the home side pouring forward late on, Forest took advantage to put one foot into the Wembley final.
The Glovers were caught on the break and when Lester's run was clumsily stopped by Forbes, Perch tucked away the resulting penalty to put Forest firmly in control for next week's second leg at the City Ground.
Yeovil boss Russell Slade:
"I don't know how we can get on the front foot next week any more than we did tonight but that is what we have to do.
"We have to regroup and come up with a game plan and be positive. Whatever happens we need to score first. That's absolutely crucial."
Nottingham Forest manager Colin Calderwood:
"It is nice to have the lead but whether it is comfortable depends. We were tested and will be again next Friday.
"We are glad to have the two-goal lead but it is severe on Yeovil for the effort they put in.
"It was enjoyable in parts, frustrating and occasionally annoying. But the players showed their ability and gave every ounce of energy throughout.
"For a period in the second half we looked as if we had a few tired legs out there."
Yeovil: Mildenhall, Lindegaard, Guyett, Forbes, Jones, Gray, Barry, Cohen, Davies, Morris, Stewart.
Subs Not Used: Behcet, Brittain, Kalala, Lynch, Knights.
Nottm Forest: Smith, Curtis, Chambers, Breckin, Wright, Perch, McGugan (Bennett 87), Gary Holt, Commons (Weir-Daley 79), Dobie (Morgan 72), Lester.
Subs Not Used: Pedersen, Bastians.
Booked: Curtis, Morgan, Commons.
Goals: Commons 23 pen, Perch 90 pen.
Ref: N Miller (Co Durham).