The former Pompey right back is expected to go into the squad for tomorrow's Rotherham game at Millmoor and said he is looking to stay at the City ground for longer.
The 26-year-old has been unable to gain first-team football at Fratton Park.
Curtis said: "They have taken over the contract I had at Portsmouth and I'll be doing my best to keep them in the Championship. It was a case of getting out of Portsmouth as quickly as I could. I wasn't disappointed with the treatment I got at Fratton Park, it was more just frustration that I wasn't getting any action for the first team."
"Being given the chance to play again at Forest is a massive boost for me and Gary Megson has made me feel wanted and I intend to repay his faith in me so im looking forward to some action against Rotherham.
Anything less than 3 points will increase Forest's chances of relegation as the teams above continue to maximize the gap between themselves.
Curtis also said "I'm aiming to secure a longer deal and im sure if I come here and do well and Forest were to stay up then that could be an opportunity for me."
Curtis has made just one Premiership substitute appearance for Pompey but made 12 league appearances while on loan with Preston. He featured in North End's 3-2 win over the Reds in October.
Curtis started his career with Manchester United and has also featured for Barnsley, Blackburn, Sheffield United and Leicester.
We at footymad wish him the best of luck.