The former French Under-21 international passed a medical yesterday and becomes Gordon Strachan's second recruit since replacing Martin O'Neill as manager, following the arrival of Guinea defender Mohamed Camara on 10 June.
"The [UEFA] Champions League was a big factor in choosing Celtic," Aliadière said. "Everybody knows the Champions League is the competition everybody wants to play in, and it would be good if I could help Celtic make an impact."
Aliadière has scored one goal in 18 Premiership games with Arsenal, whom he joined in 2001. The youngster made six substitute appearances last season after recovering from a knee ligament injury.
On Friday, Celtic also confirmed that 21-year-old forward Craig Beattie had put pen to paper on a new three-year deal. Midfield player Neil Lennon also signed a new one-year contract earlier this week and will captain the side.
Celtic will enter the Champions League in the second qualifying round after finishing second in the Scottish Premier League. They will play the winner of the first qualifying round tie between FC Kairat Almaty of Kazakhstan and Slovakia's FC Artmedia Bratislava on 26/27 July and 2/3 August.
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