Upon retirement McDermott moved into coaching at the Grimsby Institute before he was appointed assistant manager at Harrogate Town in 2010.
However, when the apprenticeship scheme was revamped he was re-signed as a trainee at Grimsby Town and after 13 appearances in the Second Division he signed professional terms.
A quote from him in 2005 on the situation of present-day footballers is: "If someone would rather sit in the reserves at a big club and drive around in a Ferrari rather than going out on-loan and playing, then I think it's a sad day.
He was appointed captain by player/manager Paul Groves, and won BBC Radio Humberside 'Sports personality of the year' award.
Further highlights followed in the 2005–06 season as he had his second testimonial against local rivals Hull City and was included in Four Four Two magazine's list of the top 50 players outside the Premier League.
[citation needed] McDermott was described by one Grimsby Town fanzine as a defender who 'defends without tackling'; meant as a compliment to his ability to shackle opposition strikers without committing fouls.
[3] McDermott played his final home game for Grimsby on 29 April 2007 against local rivals Lincoln City.
In October 2008, McDermott distanced himself from speculation linking him to managing Grimsby Town after the sacking of Alan Buckley.