On 26 March 2009 it was announced that Blackstock had signed for Nottingham Forest on loan until the end of the season, with an undisclosed fee agreed should Forest avoid relegation.
Blackstock subsequently made his debut for Forest against Barnsley on 4 April 2009 at Oakwell, scoring his first goal, the winner, for the club against Bristol City in a dramatic 3–2 win at the City Ground on 11 April 2009.

On 22 July 2009, Blackstock signed a 4-year contract with Nottingham Forest for a seven figure fee.
He scored his first goal of the season when he notched in a first round Football League Cup win over Bradford City on 12 August 2009.
He scored his first goal of the 2010–11 season in a 1–1 draw against newly promoted side Leeds United.

On 20 November 2010 Blackstock suffered serious knee ligament damage after scoring the second goal in Forest's 2–0 win at Cardiff City and was subsequently sidelined for 12 months.
He made his comeback in a friendly against York City on 14 November 2011 and scored along with Paul Anderson, another long term injured player.

In August 2011, there was reported interest from Blackpool in Blackstock.

He scored both goals, his first ones back after being injured, in a 2–1 win against Birmingham City on 25 February 2012.
Blackstock signed a new four and a half-year contract with Forest on 24 January 2013.
On 26 March 2009 it was announced that Blackstock had signed for Nottingham Forest on loan until the end of the season, with an undisclosed fee agreed should Forest avoid relegation. Blackstock subsequently made his debut for Forest against Barnsley on 4 April 2009 at Oakwell, scoring his first goal, the winner, for the club against Bristol City in a dramatic 3–2 win at the City Ground on 11 April 2009.
On 22 July 2009, Blackstock signed a 4-year contract with Nottingham Forest for a seven figure fee. He scored his first goal of the season when he notched in a first round Football League Cup win over Bradford City on 12 August 2009. He scored his first goal of the 2010–11 season in a 1–1 draw against newly promoted side Leeds United.
On 20 November 2010 Blackstock suffered serious knee ligament damage after scoring the second goal in Forest's 2–0 win at Cardiff City and was subsequently sidelined for 12 months. He made his comeback in a friendly against York City on 14 November 2011 and scored along with Paul Anderson, another long term injured player.
In August 2011, there was reported interest from Blackpool in Blackstock.
He scored both goals, his first ones back after being injured, in a 2–1 win against Birmingham City on 25 February 2012. Blackstock signed a new four and a half-year contract with Forest on 24 January 2013.
Dexter Blackstock