On 30 August, Turner passed a medical and agreed a three-year deal with Cardiff City. The move was finalised the following day where he signed for an undisclosed fee, reported to be £750,000. Turner's knee injury, suffered the previous season, kept him out for the first few games following his move, though he made an appearance for the Development Squad against Southampton on 13 September, an encounter which ended in a 1–0 defeat for the Bluebirds. Turner's first involvement with Cardiff's first team was as an unused substitute against Southampton in the Championship on 28 September. His debut came on 1 October 2011, coming as an 84th-minute substitute against Hull City. His first start came two weeks later in 2–2 against Ipswich Town. He made his 100th career appearance on 30 October, against Leeds United. Turner's first goal for Cardiff came on 17 December 2011, in a 3–2 defeat to Middlesbrough. His 100th league appearance came on 31 January, in 1–1 draw with Southampton.