Both drivers had driven for the squad, which won the teams' championship in 2010, in the recent pre-season test at Barcelona.
Their announcement means just one seat, at Venezuela GP Lazarus, is still to be confirmed ahead of next weekend's season opener in Malaysia.
Dillmann, German F3 champion in 2010, scored a podium for iSport when he made his GP2 debut in last year's non-championship series final in Abu Dhabi.
The 22-year-old Frenchman said he wanted to be competitive from the beginning.
"I'm delighted to sign in GP2," Dillmann said. "It hasn't been easy but I never gave up and step by step went my way up here.
"It will be my first year with "big cars" but i don't want to see it as a 2 or 3 years plan, my goal is to be competitive from the beginning, I know how tough it is to just have the chance to race in GP2.
"We have a good connection together with the team since our first test and I'm really looking forward to start the season."
Teixeira meanwhile returns to GP2 after spending 2010 competing in Formula 2 and 2011 as a test driver for the Lotus - no Caterham - F1 squad. His 2009 GP2 campaign with Trident yielded a best finish of 14th.
"I would like to say thank you to all the Team for the opportunity they gave me to test in Barcelona," Teixeira said.
"I think I can learn a lot during this year with them and I'm sure together we can achieve good things. It's an amazing feeling to come back to racing after a big stop, especially with the opportunity to drive a nice car like this and be part of such good team."