Mike Phelan began his career at Burnley, signing as an associated schoolboy in July 1979, as an apprentice two years later and as a professional in July 1980. He made his league debut in January 1981 against Chesterfield and whilst at Turf Moor would gain England Youth caps and a Third Division champions medal. 168 games for Burnley brought him to Norwich's attention who signed him on 30th May 1985. A strong, influential midfielder was needed if Norwich were to return to the top flight following their relegation to Division Two in May 1985. Mike lived up to the expectations and City won the Division Two championship in his first season at the club. He became club captain when Steve Bruce joined Manchester United and led the Canaries to 4th place in Division One in 1988/89 and a place in the FA Cup semi-finals..

He was called into the England squad for the Rous Cup games against Chile and Scotland but did not play due to a hamstring injury. Mick's success drew the attention of the big clubs and he followed Steve Bruce to Old Trafford for £750,000. Whilst with Manchester United, he won his first international cap (against Italy) and a FA Cup winner's medal in his first season. Unlike Steve Bruce, Mike was unable to establish a regular spot in the United first team and so dropped down a division to join West Bromwich Albion in 1994 .

He returned to Carrow Road in December 1995 as Assistant Manager to Gary Megson. and managed the City Reserves. When Megson was fired and joined Blackpool, Mike followed him returning to his native North-West. He has since accompanied Megson to Stockport County. His career total stands at Burnley (168 league games, 9 goals), Norwich City (194 games, 10 goals), Manchester United (102 games, 2 goals) and West Bromwich Albion (21 games)

Following Megson's sacking as Stockport boss on 25th June 1999, Mike was been named as a potential successor to the post although Chris Kamara and Youth team boss Andy Kilmer were considered more popular choices. Mike lost out to Andy Kilmer but has remained as Assistant Manager according to the Rothmans Football Yearbook 1999/2000. Mike didn't stay long under Kilmer's regime, quitting his position and taking up a role at Manchester United's Centre of Excellence. With Steve McClaren's departure to Middlesboro in the summer of 2001, Mike was promoted to first team coach.

United's below-par start to 2002/03 was turned around in November when Phelan was promoted from reserve team manager to become Fergie's second lieutenant. In his first match on the bench, United beat Newcastle 5-3 and the Red Devils went on to win the next five games and eventually snatch the Premiership from Arsenal.

Ferguson's number two Carlos Queiroz left Old Trafford in the summer to take over the reins at Real Madrid. Rather than rush into appointing a new deputy, Ferguson entrusted Phelan with the role. A successful pre-season tour of the USA, a Charity Shield victory and a strong start to the 2003/04 campaign suggests a wise move by the wily Scot.

"The manager has said he is not rushing into anything, he gave me an opportunity to do pre-season and it has gone pretty well," said Phelan. " The manager is happy with what he has seen and we will have to see where that goes."

Mike was linked with the managerial vacancy at Burnley in May 2004 following their sacking of manager Stan Ternant.

In September 2008, Mike was appointed Assistant Manager following the departure of Carlos Queiroz to manage the Portuguese national team. Sir Alex Ferguosn said "Mick knows Manchester United inside out, having been associated with the club for the best part of 20 years. I am delighted that Mick and Rene [Meulensteen - new first team coach] have agreed to fill these important positions.Mick is a very talented and professional coach, whose ability and contribution to the club's success has often been understated."

Phelan and United won the Premiership trophy in 2008/9, 2010/11 and 2012/13.

Phelan left Old Trafford in May 2013 following the retirement of Sir Alex Ferguson and the appointment of David Moyes as his successor.

In November 2013, the Daily Star reported that Phelan was being lined up by the Norwich City board as a replacement for struggling maanger Chris Hughton. Phelan also claimed that he took charge of most of the first-team responsibilities himself, albeit "undercover", while Alex Ferguson took the plaudits. "My first thoughts are to be the boss," Phelan told the Daily Mail, having been asked about a return to football. "It’s the progression for me now. That’s what I’ve been doing for the last five years, albeit with the title of assistant boss. [Ferguson] was the head of the establishment, there’s no doubt about it and rightly so. He didn’t get to where he’s got through not being a big decision maker but he’ll be the first to admit that a lot of people played their part in that. "We all were undercover in that respect. We weren’t the face of what was going on but that was our job."

Phelan returned to Norwich on 20th November 2014 as first team coach replacing Mark Robson. "It was important for us to try and get the best coach we could," Neil Adams told BBC Radio Norfolk."I think Mike's record and experience speak for themselves. I've worked with him here. He'll be working with myself, Gary Holt (first-team coach) and Tony Parkes (goalkeeper coach) out on the grass on a daily basis. He is not a director of football or anything like that - he is a first-team coach."

Phelan was placed in charge of the City first team when Neil Adams resigned on 5th January 2015. Although favourite for the City job, this went to Alex Neil. After one game working together, Phelan resigned and joined Hull City on 5th February 2015 as assistant to Steve Bruce, replacing Steve Agnew who joined Middlesbrough. .Bruce said "He comes in at just the right time to add valuable experience, plus he has been assistant to the best boss we will ever come across."

Phelan, Bruceand Hull were relegated from the Premiership on 23rd May 2015 when they could only draw with Manchester United whilst rivals Newcastle secured safety with a win over West Ham. They won promotion back to the Premier League on 28th May 2016 via a play off final victory over Sheffield Wednesday.

Phelan was put in temporary charge following the departure of Bruce and Bertschin from Hull in the summer of 2016 and led the team in their first game in the 2016/17 Premier League season. A good start saw the 54-year-old named manager of the month for August. n September, Phelan revealed he was offered the job on a full-time basis but there had since no contact amid the club's search for a new owner.He was finally appointed as head coach on 13th October 2016 but his next game saw them lose 6-1 to Bournemouth.

Phelan though was sacked on 3rd January 2017 with Hull in the relegation zone having picked up only three points in their previous nine games. He was replaced by Portuguese boss Marco Silva.

He began working as Sporting Director for the Australian side Central Coast Mariners but returned to Manchester United on 19th December 2018 as first team coach alongside caretaker manager Ole Gunnar Solskjaer who had been appointed to replace Jose Mourinho. Ed Woodward, Executive Vice Chairman, said: "Ole is a club legend with huge experience, both on the pitch and in coaching roles. His history at Manchester United means he lives and breathes the culture here and everyone at the club is delighted to have him and Mike Phelan back. We are confident they will unite the players and the fans as we head into the second half of the season.” He continued to work with the Mariners during this period.

On 16th May 2019 it was reported that Phelan would not continue his commitments with the Mariners as he had been permanently appointed as Manchester United's Assistant Manager, signing a three year deal.

He was relieved of his coaching duties on 10th July 2022 with the arrival of new manager Erik ten Hag. It is thought that he will remain in an ambassadorial role with the club.