Otis Khan notched his second goal in three pre-season games to help see Town leave Stebonheath Park with a victory.
In a game dominated by the Glovers, the tricky winger found the back of the net with a first-half free-kick as the visitors engineered copious opportunities against their Welsh opponents.
Second half substitute Francois Zoko doubled the lead late on, as preparation for the 2017/18 season continued.
Darren Way made three changes to the side that started against Bristol City at the weekend, handing Omar Sowunmi and Olufela Olomola their first starts in pre-season as well as an unnamed trialist.
The trio of Keston Davies, Zoko and Connor Smith started on the bench, alongside defender Tom James who featured for the first time in pre-season having recovered from concussion picked up in training.
With four of the Glovers new signings on the pitch from the start, one of them almost broke the deadlock inside the opening 60 seconds
Southampton loanee Olufela Olomola, who scored Yeovil’s solitary goal at the weekend, brought down Jake Gray’s ball over the top before whistling an effort just wide of the target.
As expected, Way’s side saw plenty of possession in the opening 45 minutes and went close again with four minutes on the clock as Sowunmi failed to direct James Bailey’s corner on target.
In a rare foray into the Glovers half the hosts tested stopper Jonny Maddison when Jordan Davies saw an audacious lob tipped over the bar, before the action returned to the other end as Olomola went close again to testing Craig Morris in the home goal.
After a frantic start, Yeovil took the lead midway through the half when Otis Khan’s free-kick from just outside the box on the left evaded everyone in the middle and nestled in the back of the net.
With a deserved lead, the Green and Whites spurned a chance to double their advantage before the half-hour mark, after Nathan Smith was hauled down in the box by Anthony Finselbach for a penalty.
Summer signing Rhys Browne stepped up from 12 yards, but saw his effort tipped onto the post by a sprawling Morris to keep it 1-0.
As the game ticked towards the break Khan almost added a second from 25 yards as his venomous shot flew just wide, forcing Town to settle for a single goal lead at half-time.
Those who headed down the tunnel didn’t re-emerge for the second half, with Way making 11 changes as seven trialists accompanied Davies, James, Smith and Zoko for the second 45.
Despite the mass changes the pattern of the match continued, as experienced striker Zoko was twice denied by Llanelli’s stopper with smart saves from close range as the game ticked past the hour-mark.
Having brought on young ‘keeper Kai Rees, the hosts continued to hold firm as two Town trialists were denied in quick succession by the home stopper, with the Glovers still entrenched in the Reds half.
But with the last kick of the game Town made it 2-0 when Zoko was rewarded for his persistence in the second half with a goal of his own to continue the Glovers pre-season with a victory.
Yeovil Town: Maddison (Trialist 46’), Mugabi (Trialist 46’), Sowunmi (Davies 46’), Smith (James 46’), Dickson (Trialist 46’), Browne (Trialist 46’), Bailey (Smith 46’), Gray (Trialist 46’), Khan (Trialist 46’), Olomola (Zoko 46’), Trialist (Trialist 46’).
Llanelli Town: Morris (Rees 46’), Graves, Finselback (Jones 30’), C. Thomas, R. Thomas, Clarke, Bevan, Davies, Samuel, Loveridge, Trundle.