Rangers have signed Brazilian midfielder Emerson on a pay-as-you-play deal despite rival bids from Celtic and Wolverhampton Wanderers.
Emerson trained with Rangers on Friday
And the Ibrox club are hoping to tie up a loan deal for Valencia striker John Carew for the rest of the season.
Emerson comes as a replacement for skipper Barry Ferguson, who is being sold to Blackburn Rovers for £7.5m, and has signed a two-year deal based on appearances after completing a medical.
The 31-year-old former Middlesbrough, Deportivo La Coruna and Atletico Madrid midfielder had held talks with both Wolves and Celtic before opting for the Scottish champions.
Rangers manager Alex McLeish, who also on Friday allowed Australia defender Kevin Muscat to join Millwall, told Rangers' website: "I'm delighted to have completed the deal to bring Emerson to the club.
"I went to watch him playing for Atletico about three weeks ago and we have had some very good reports on him, especially from Bryan Robson."
Robson was the boss at Boro when Emerson arrived at the Riverside for a brief spell alongside fellow countrymen Juninho and Branco.
Emerson has signed in time to play in the Champions League and may even make his debut at Tannadice against Dundee United on Sunday.
"I don't expect him to be the same player as Barry Ferguson, but he will bring us marvellous experience," said McLeish.
"We don't want to lose key players and we didn't want Barry Ferguson to go. It was not a Rangers decision."
Rangers instead want to strengthen their squad further but face competition from Everton and Roma for the signature of Norway international Carew.
McLeish hopes that Champions League games against Manchester United, Panathinaikos and Stuttgart will be his trump card.
Emerson's departure from Middlesbrough came amid reports that, among other things, he was unhappy with the climate in the north-east, but McLeish is not expecting problems.
Wolves thought the player was on his way to Molineaux, after Emerson agreed terms and underwent a medical with the Premiership newcomers.
The English club said on Wednesday that they were close to tying up a deal for Emerson, who spent last season at Atletico, following a £4m move from Deportivo La Coruna.
But the switch was held up by a dispute between the player and the Spanish club and that gave the agents of the 31-year-old Brazilian time to alert other clubs.
Celtic manager Martin O'Neill indicated that Emerson's wage demands had been a stumbling block.
"It wasn't just an enquiry, but it doesn't really matter," he said. "We are moving on and I am always thinking of the possibility of something materialising before Sunday's deadline."