He has managed in the top three divisions of English soccer with Walsall, Brentford and Aston Villa. Smith has won three Manager of the Month awards, one with Walsall and two with Villa.

Smith's playing career began at Walsall in 1989, but his first season was not a success as they were relegated to the Fourth Division. The defender ended up spending five seasons with the Saddlers, during which the side flirted with promotion but never achieved this goal. After the 1993/94 campaign, Smith was on the move, having played 166 times and scoring twice.

In the summer of 1994, Smith was sold to Hereford United for a club-record fee of £80,000. Manager Graham Turner named Smith captain and the club made it to the Third Division play-offs in 1995/96. Despite a goal from Smith in the first leg, Hereford lost 4-2 to Darlington in the semi-finals.

A year after making the play-offs, the Bulls were relegated from the Football League, losing out to Brighton and Hove Albion by the narrowest of margins. Both sides had finished the year on the same number of points and despite Hereford having the superior goal difference, they had scored fewer goals, and it was this metric that decided league table position.

After making 146 appearances with Hereford, Smith joined Leyton Orient in August 1997. In the 1997/98 season, he played 51 times and scored 10 goals, the most goals he had scored in a single season at that point. The following season, Smith was named club captain and led his side to the Third Division play-off final where they lost 1-0 to Scunthorpe United.

In the 2000/01 campaign, Smith led his side to the play-off final for the second time in three years but sadly for Orient the outcome was the same. Despite taking the lead twice, Orient lost 4-2 to Blackpool.

Smith left the club in the middle of the 2002/03 season having made over 300 appearances and scoring over 40 goals.

For the first time in his career, Smith played in the First Division after joining Sheffield Wednesday in February 2003. It was a short stay in the second tier of English soccer for Smith as the Owls were relegated after finishing 22nd. Smith spent just 18 months in the Steel City as he was released at the end of the 2003/04 season. His record reads one goal in 62 games for the Sheffield side.

Smith ended his playing career with Port Vale, making just 13 appearances before going back to Leyton Orient to become a youth team coach in January 2005.

As youth coach at Leyton Orient, Smith attained his UEFA Pro Licence in 2008 and a year later, he returned to Walsall as Head of Youth. In January 2011, Smith was appointed caretaker manager after the dismissal of Chris Hutchings. Two-and-a-half weeks later, Smith was announced as the Saddlers' new permanent manager.

Smith took over the job with his side nine points adrift at the bottom of League One and by the end of the season, he had taken his side out of the drop zone. His first win at the club was the Saddlers' best since 1986, as Walsall beat Bristol Rovers 6-1. The following year his side went on a nine-game run with just one defeat, but seven of these matches were draws and they would go on to finish in 19th place.

In 2012, Smith signed a new two-and-a-half year deal after the club announced a £10,000 profit due to Smith's "Total Football" approach, which drew praise from fans and pundits. In January 2013, Walsall won four out of five games and Smith was named Manager of the Month. They finished ninth in this campaign.

In 2015, Smith took Walsall to the final of the Football League Trophy where his side lost 2-0. They may have lost but it was a moment of history for the Saddlers as it was the first time they had played at Wembley Stadium. At the end of the season, Smith was awarded a Special Achievements Award by the League Managers Association.

In November 2015, Smith left the Saddlers to join Championship side Brentford. At the time of his departure, Smith was the fourth longest-serving manager in the Football League.

Known as the 'Ginger Mourinho', Smith spent two seasons with the Bees and continued to implement his attacking and attractive style of play. At Brentford, Smith did not have a huge budget but during his last season (2017/18), his side finished in ninth place.

In October 2018, Smith was appointed the new manager of Aston Villa. He revolutionised the side, taking them from 14th in the Championship when he took over into the play-off places by the time the season had finished. After Jack Grealish returned from injury, Smith gave him the captaincy and the 23-year-old inspired his side in the final weeks of the season.

In March 2019, Smith was named Championship Manager of the Month after overseeing five straight wins including victory in the Second City derby against Birmingham City. His side also broke a 109-year club record for the longest winning streak, scoring 10 straight victories. Things got even better as  Smith's side beat Derby County 2-1 in the Championship Play-off Final to secure promotion back to the Premier League after a three-year absence.

In the summer of 2019, Smith oversaw rebuilding at the club as they spent £144.5million to help them adjust to life back in the Premier League. With four games remaining, they were four points adrift of safety but managed to secure survival on the final day of the season. Meanwhile, in the EFL Cup, Villa made it all the way to the final before losing 2-1 to Manchester City. In November 2019, Smith had signed a contract extension that would keep him at the club until 2023.

Smith brought in more reinforcements in the summer of 2020 and this paid off as Villa got off to their best start to a season since 1930. This included a 7-2 home win over reigning Premier League champions Liverpool. It was the first time a side had scored seven goals against the league winners in 67 years. Villa couldn't continue their fine run of form though and finished the 2020/21 season in 11th.

Villa lost their star man Grealish in the summer of 2021 as he joined reigning champions Manchester City for a British record of £100million. Smith brought in Leon Bailey from Bayer Leverkusen and Emiliano Buendia from Norwich City as replacements.

Smith has a wife called Nicola and together they have two children, a son and a daughter. Smith is a childhood Villa fan and his dad worked as a steward at Villa Park before passing away in May 2020.

According to sportmob.com, Smith's salary with Villa sees him earn more than £1million a year and his total net worth is more than £8million.