|Date of birth||2 November 1962|
|Place of birth||Liverpool, England|
|Height||1.85 m (6 ft 1 in)|
|2000–2001||Cork City F.C.|
|* Senior club appearances and goals counted for the domestic league only.
His time at top-flight clubs Everton and subsequently Aston Villa were where he gained most fame, as Everton enjoyed successful periods at this time. Aston Villa pushed for honours during the early 1990s.
After turning professional, Liverpool-born Mountfield spent a season-and-a-half at local club Tranmere Rovers before moving across the Mersey to play for Everton. He signed for £30,000 prior to the 1982–83 season.
A fast and strong defender, Mountfield was a composed footballer who could make important contributions at both ends of the pitch.
At Everton he formed a defensive partnership with fellow defender Kevin Ratcliffe and the club leapt to FA Cup glory in 1984 against Watford, followed by League Championship glory in 1984–85. Everton also reached the FA Cup final that season, and won the European Cup Winners Cup in Rotterdam. He also won another League Championship winners medal in 1987. In league matches, he scored an average of one goal every 5.6 matches – an incredible average for a defender. In one season, he scored 14 goals in all competitions.
However, his first team chances became limited at Everton following the arrival of Dave Watson in August 1986, and injuries didn't help his chances of first team football either.
After appearing in just nine out of 40 First Division games for Everton in 1987–88, a £400,000 fee took him to newly promoted Aston Villa in June 1988. He was a regular in the Villa defence for the next three years, helping secure their First Division survival in 1988–89. In 1989–90, it looked as though Mountfield would add another league title medal to the two he won with Everton, as Villa topped the First Division on several occasions, but eventually they finished second behind champions Liverpool.
However, the appointment of Ron Atkinson as Villa manager in June 1991 signalled a new era at Villa Park, and Mountfield was not part of Atkinson's plans as he bought Shaun Teale to partner Paul McGrath in the centre of defence, and Mountfield made just two more appearances for Villa before joining Wolverhampton Wanderers in November 1991.
He stayed for three-and-a-half years, playing 80 league games, but after 1994 his career was spent outside the top two tiers of English football. He first spent a season with Carlisle United, helping them win promotion to Division Two as Division Three champions, before a brief spell at Northampton Town.
He then began a spell as player, coach and captain of West Midlands side, Walsall. Indeed, such was the measure of respect he was held in by many at the club, he was one of the favourites to replace Jan Sorensen as manager in the summer of 1998. However, the job went to former Aston Villa winger Ray Graydon, and Mountfield left the club to pursue his managerial ambitions.
Mountfield was selected to participate in the 1984 UEFA European Under-21 Football Championship. He made his début at Bramall Lane in the second leg of the final versus Spain which England won 2–0. England beat Spain 3–0 on aggregate. It was the only England U21 cap that Mountfield received.
He represented England at 'B' level later in his career.
In 2000, League of Ireland team Cork City appointed former Shelbourne boss Colin Murphy (footballer) as successor to local legend Dave Barry. Colin Murphy stayed for one Super Cup game before departing to Leicester City. In the lurch, facing a UEFA Cup tie in Lausanne, the club brought in Mountfield. Mountfield had a turbulent ride in his first managerial appointment, the team lacking consistency, goals and luck. After relative success in preceding seasons crowds again dwindled as the team struggled and the increasingly unpopular Mountfield was sacked in January, after just six months in charge and a 4–0 defeat at home to St Patrick's Athletic. Liam Murphy took over and the team embarked on a 13-game unbeaten run that brought an Intertoto ticket and a tenth Munster Cup success. Mountfield is today remembered by some in Cork as a manager was ahead of his time – Cork City had not yet become a fully professional side and rumours abounded of Mountfield's unpopularity with some of the older semi-pros in the squad. Cork would finally make the leap to professionalism in a few years, attaining the League title in 2005, with Mountfield's first signing, goalkeeper Mick Devine an integral part of the side's great defence which earned them the title.
From 2010, Mountfield worked as a PE Teacher for Poulton Lancelyn Primary School in Spital, Wirral. He now, however, works as part of the PE staff at Pensby High School, a specialist Sports College, Wirral. He also is teaching a course at, St Mary's College, Crosby on Multi Skills with 25 students, Learning to become Sports Leaders
He is also working for BBC Radio Cumbria as part of their Carlisle United commentary team.