Senior producer James Nance said it had to "grow up" in order to "resonate" with a wider audience.
"We're under Visceral's offices now, so that means injecting a bit more story and serious tone," he told Digital Spy at gamescom in Cologne, Germany.
"We're known for Dead Space, now we want to be known for this as well. It's about quality and bringing epic moments to bear.
"Part of that was having the franchise grow up a little bit. The old Army games had humour and we have humour too in a buddy cop sense, and we use the humour to alleviate tension, because the storyline gets serious at times."
He continued: "But we wanted to move away from the fist-bumping, frat boy-type hero we had before, because some people found it really funny and really charming, but it didn't resonate with everybody.
"We think that we're broadening our audience and our appeal by bringing it up a little bit."
Announced earlier this month, the third game in the co-op franchise takes on a more mature and grittier tone, as the mercenaries Alpha and Bravo take to the streets of Mexico amid a deadly drug war.
It is being developed by Visceral Games in Montreal, formerly EA Montreal, which developed the previous Army of Two titles. It will use the Frostbite 2.0 engine, which powered games like Battlefield 3.
Army of Two: The Devil's Cartel will be available for Xbox 360 and PlayStation 3 in March 2013.
> Read Digital Spy's review for 'Army of Two: The 40th Day'
Watch the gamescom trailer for Army of Two: The Devil's Cartel below: