Following Lee Clark's departure in December 2008 to join Huddersfield as manager, Norwich manager Glenn Roeder recruited Adam Sadler to be Norwich's first team coach in cojnuction with Paul Stephenson. Roeder said "in Adam Sadler I know I have a coach of the same ability who has had to learn the game from the bottom.“He will qualify for his Pro licence next month at the same time as Lee. It's a huge feather in his cap to qualify for that at 29.”

Roeder knew Sadler from his time as Newcastle Manager where Sadler was appointed to Roeder's coaching team. Sadler was youth coach then assistant Academy Director at Newcastle before being appointed to lead Newcastle's reserve team. He left Newcastle in September 2008 when Kevin Keegan quit.

Prior to his coaching career, Sadler had been a youth team goalkeeper at Newcastle and also spent time with Manchester United and Barnsley.

Sadler was sacked by Norwich City on 14th January 2009 following the club's poor run of performances which also led to Roeder's departure

In June 2009, Sadler returned to the North East joining Blyth Spartans as Assistant Manager to Mick Tait; replacing Harry Dunn and Graham Fenton, who left the club at the end of the 2008/9 season

Sadler joined Plymouth in the summer of 2010 to coach the Under-18s following the departure of Mike Pejic but with the departure of John Carver and Paul Mariner, he took on additional responsibilites assisting manager Peter Reid

In August 2011, Sadler joined Manchester City as their Under-18 coach to work with the youth side under the watchful eye of Academy manager Scott Sellars.

He then spent some time with Ukrainian side Tavriya Simferopol.

In 2014, he joined Leicester as a tactical analyst before being promoted to a first team coach position in the summer of 2017. On 24th February 2019, he was placed as caretaker manager alongside Mike Stowell following the sacking of Claude Puel.

On 28th August 2021 he joined the backroom staff of the Northern Irish national team in conjunction with his role at Leicester.

Sadler left Leicester at the beginning of July 2023 following the appointment of Enzo Maresca as Head Coach who brought in his own staff.

On 31st December 2023 he joined Celtic as First Team Coach.