Dmitri Halajko joined Norwich City's academy in the summer of 2012. He had previously been the Football Association's head of coaching development in the Eastern region. Prior to this, he had worked for Colchester United's centre of excellence for 11 years.

After a year working with the FA, he returned to Norwich to assist Under-18s manager Jerry Gill as Professional Development Coach. In December 2014, a restructuring within the academy saw him appointed as Lead Phase Coach for the Professional Development Phase with the team coaches Graeme Murty (Under-16s), Jerry Gill (Under-18s) and Paul Wilkinson (Under-21s) working under him. His role is to make sure now that rather than having three teams there is one group of players, considering them as a group rather than three different strands.

In August 2015, he was appointed to the role of managing Norwich's Under-21s, assisted by Darren Huckerby.

It was announced at the beginning of February 2015 that Halajko would be leaving Norwich for a senior operations role with a Premier League side. This was later revealed to be Leicester City.

On 2nd July 2019, it was reported that Halajko had joined West Ham as their Lead Academy Under-23 coach having been recruited by former City colleague Ricky Martin. Martin told West Ham's website: "I am really pleased that Dmitri has agreed to join us and it is a real coup to have appointed someone of his experience and ability.I have seen at first hand his quality and talent as a coach, both in sessions on the training pitch and working with players individually on their development programmes. He has fantastic experience at academy level and a proven record of progressing elite players through to first team level. His style and approach will fit in perfectly to the West Ham way that we encourage and nurture here at Chadwell Heath."

Dmitri left West Ham in November 2021 to take up a youth and coaching development role at the Premier League. He was replaced by Mark Robson.

On 11th July 2022, Halajko returned to Colchester United as Sporting Director, a newly created role in a backroom shake-up that saw Steve Ball named as Technical Director. Halajko was placed in charge of the recruitment process for a new manager after Colchester sacked Wayne Brown in September 2022. He said "One of the key things we're looking for is that we're a development club and we want to develop the senior players we've signed and our young players and put them into our squad and give them opportunities."

On 22nd August 2024 Dmitri left Colchester to become Academy Director at Ipswich Town, replacing Dean Wright who left in June 2024. At Colchester he had worked on the appointment of several head coaches such as Danny Cowley and Matt Bloomfield, played an integral role in recruiting the likes of Jayden Fevrier and Jay Mingi who have since been sold to higher-league clubs along with the club's 11 signings this summer and ensuring a smooth pathway between the club’s first team and academy.

Ipswich Chairman Mark Ashton said: “After an extensive recruitment process led by Luke Werhun (Chief Operating Officer) and Gary Probert (Director of Football Operations), Dmitri demonstrated his history of producing high-level players and other industry experience, we knew he would be a great fit for us. Dmitri has held senior leadership roles within Premier League clubs and Category One Academies, and will now help us to drive standards and help us achieve our goal of becoming a Category One Academy. Dmitri will also help to build on the progress already made in our Academy to keep improving our players, people and programmes.”