Both men played under former Spurs boss Harry Redknapp at White Hart Lane and will stay at Loftus Road for the rest of the 2013-14 campaign as the Hoops plot an instant return to the Barclays Premier League.
Left-back Assou-Ekotto, who is currently on international duty with Cameroon, told the club's official website: "It is fantastic to be linking up with Harry again.
"I enjoyed my best form at Spurs under him and am looking forward to doing my best for QPR.
"I know the way Harry likes his sides to play, and it is a style that suits me which is why I am excited about this opportunity.
"QPR have made a great start and I can't wait to help them build on that during my time here."
Redknapp was equally enthused about bringing 21-year-old midfielder Carroll to the club.
"He's a player I fully expect to go to the very top of the game - he's a future England international," he added.
"I played him at Spurs in Europe and he was fantastic for me. He's got all the attributes to be a top, top player.
"He can pass, he can create, he can score goals - he's a fantastic player and I'm confident he'll flourish here for us."
Rangers also beat the deadline to bring in Croatia international Niko Kranjcar on a season-long loan from Dynamo Kiev.
The 29-year-old has played under Redknapp at Portsmouth and Tottenham and he will stay in west London for the remainder of the 2013/14 campaign.
"Niko's a crowd pleaser - he gets people off their seats," Redknapp said.
"He's a top player and someone who will add great quality to the squad.
"He can play in a variety of positions - off the front-man, out wide on either side - and he's always a threat.
"He gets at players and makes things happen.
"He's someone I obviously know a lot about and he'll be a fantastic addition for us."