On 5 August 2009, Liverpool announced that they had agreed a deal with Roma for the transfer of Aquilani, subject to a medical.[11][12] The club subsequently announced that the player had passed the medical and signed a 5 year contract on 7 August 2009.[13] Roma revealed that the fee was €20 million (£17 million) plus sporting bonus.[14] Aquilani was handed the number 4 shirt, last worn by Sami Hyypiä, who joined Bayer Leverkusen at the end of the 2008–09 season. Although it was initially thought that he was recruited as a replacement for deep-lying playmaker Xabi Alonso who had left the same summer to join Real Madrid, Aquilani actually prefers to play further up the pitch and is considered to be more of a dynamic attacking midfielder than a holding playmaker.
Aquilani made his Liverpool reserves debut with a 15 minutes substitute appearance in a 2–0 win against Sunderland reserves on 21 October 2009.[15]
Aquilani's first game for Liverpool was a 2–1 4th round Carling Cup defeat to Arsenal, coming on in the 77th minute for Damien Plessis.[16] He made his long awaited Premier league debut on 9 November 2009, as a late substitute against Birmingham City in a 2–2 draw.[17] He then made a 30 second appearance against Hungarian club Debrecen on 24 November which Liverpool won 1–0 courtesy of a goal from David Ngog. Aquilani made his first start against Fiorentina in a Champions League match on 9 December 2009, where Liverpool lost 2–1.[18] Aquilani made his first Premier League start against Wolves on 26 December 2009 and received a standing ovation from the Kop when he was substituted in the 84th minute for Daniel Pacheco.[19]
Aquilani next started for Liverpool in their 2–0 win over Bolton Wanderers, where he got his second assist for Liverpool, again setting up Dirk Kuyt. He scored his first goal for Liverpool on 15 March 2010 against Portsmouth and he also assisted Fernando Torres for the fourth Liverpool goal. He was voted man of the match by the fans on Liverpool's official website. Aquilani also gained the man of the match award in his next Liverpool league start, against Fulham in a goalless draw at Anfield. In his next start for Liverpool he finished the match with three assists during a 4–0 away win against Burnley On 29 April 2010 he scored a goal against Atlético Madrid in the Europa League, cancelling out Atlético's first leg goal from Diego Forlán by scoring moments before half-time. Despite a great performance from Aquilani on the night, Liverpool eventually went out of the semi-finals on the away goal rule after Yossi Benayoun had put Liverpool 2–0 up, as Forlán scored his second of the tie in exta-time to take the aggregate score to 2–2.[20] Aquilani won the LFC Man Of The Match award again after his performance.[21] Aquilani also played in Liverpool's last 2 games of the season, a 2–0 defeat at the hands of Chelsea at Anfield[22] and a goalless draw away to Hull City at the KC Stadium.[23] In total, Aquilani played 26 times in his debut season for the reds, scoring twice but rarely playing the full 90 minutes.
With the departure of Rafael BenÃtez to Internazionale in June 2010, new manager Roy Hodgson played him in some pre-season games, but stated publicly in mid-August that Aquilani may go back to his native Italy on loan for a full season, where playing regularly he could gain match fitness.[