The former St Mirren forward has been with the Irn-Bru First Division side since November after having agreed a short-term deal following a trial period at Firhill.
His contract is set to expire next month, but McNamara is keen to retain the 33-year-old as the Jags look to build on their encouraging recent form in the second half of the season.
Dargo, who missed Monday's 1-0 win over Queen of the South due to injury, has yet to score for Thistle. But he has impressed at the head of the Jags' attack, adding vital experience to McNamara's strike options.
The ex-Kilmarnock and Inverness Caley Thistle player could return to the Thistle side when they face Ross County on Monday, and McNamara hopes a deal can be struck to keep the striker at Firhill beyond the end of his current deal.
He said: "I will need to speak to the board and see what the finances are like. I think Dargs has done well since he has come in to the club.
"He adds a bit of experience to the team and hopefully that benefits the other strikers we have, not just in games but in training as well.
"It will come down to money, but we'll see what we can do."
Despite Dargo's absence on Monday, Thistle bounced back to winning ways with a vital win over Gus MacPherson's side to set up a crunch clash with league leaders County next week.
A Kris Doolan header just after half-time clinched the win for the Jags as they closed the gap on third-placed Dundee to just one point.
County's draw with Falkirk means Thistle are just 10 points adrift of Derek Adams' side ahead of their trip up the A9 and McNamara is targeting a Highland triumph to further reduce the deficit to the Staggies.
He said: "It is always a difficult game, but it is important that we go and try and win the game and narrow the gap.
"We want to try and get as close to them as we can. They will be favourites with the game being at home but, like every other game, we will go there looking to win.
"We know how hard County will be to break down. They are very solid at the back and have a lot of experience in their team, especially at the back.
"It is important we go up there and be positive and try and take the game to them."
Thistle have taken just one point from their two meetings with County so far this season but have been left with feelings of what might have been.
Goals from Paul Cairney and Chris Erskine clinched a dramatic point at Victoria Park in September and McNamara admits the Jags can ill-afford to hand County a two- goal start this time around.
He said: "We gave ourselves a mountain to climb the last time we played there. We were 2-0 down at half time but showed great character to come back into the game and get a point.
"They had a man sent off, which did change the game, but we could have gone on to win it in the end.
"There has not been much in the games between us this season, but we are coming off a good result against Queens on Monday and are looking to go on a wee run again to keep pace with the top."