At club level, he served as manager of Ajax, Barcelona, AZ Alkmaar, Bayern Munich and Manchester United, as well as having three spells in charge of the Netherlands national team.

Van Gaal is one of the most decorated managers in the history of the game, having won 20 major honours in his managerial career at club level, contrasting with his mediocre results coaching the Dutch national team.

Despite announcing his retirement due to family reasons in 2019, Van Gaal returned to management in August 2021, when he was appointed as head coach of the Netherlands for a third time.

[11] After four years spent in Belgium, he returned to his homeland and made his Eredivisie debut for Telstar under the guidance of manager, Mircea Petescu, whom he followed to Sparta Rotterdam.

[18] Van Gaal moved to Barcelona in 1997, taking over from Bobby Robson, and helped the team win two La Liga titles (1997–98, 1998–99) and the Copa del Rey once.

He expressed that it was difficult to implement his football philosophy at Barcelona due to cultural differences, and that he struggled hard as some players were unwilling to follow his lead.

In 2001, the Netherlands beat Andorra, Cyprus and Estonia, but despite leading group leaders Portugal 2–0 with seven minutes left, drew 2–2 and fell three points behind second-place Republic of Ireland, who were unbeaten.

Van Gaal also led AZ to a runners-up finish in the 2006–07 KNVB Cup and lost a 2007–08 Champions League qualification play-off to Ajax 4–2 on aggregate.

[38][39][40] Van Gaal got off to a poor start as Bayern coach, winning only one of his first four matches in charge, and by November the club was on the brink of a Champions League group stage exit following two losses to Bordeaux.

[41] Van Gaal installed many youth players as fixtures in the starting 11, including Thomas Müller and Holger Badstuber, and also converted the winger Bastian Schweinsteiger into a defensive midfielder.

[44] In the Champions League, Bayern won 4–4 on the away goals rule in the quarter-final against Manchester United[45] and 4–0 on aggregate against Lyon in the semi-final,[46] securing them a spot in the final, where Van Gaal was to meet his former pupil and assistant at Barcelona, Internazionale coach José Mourinho.

[55] "I am happy that the KNVB approached me", said Van Gaal, who was assisted by former Dutch internationals Danny Blind and Patrick Kluivert, both part of his successful Ajax squad from 1995.

"[56] Van Gaal led the Netherlands through its 2014 World Cup qualification group as the team won nine and drew one of their ten matches with a goal difference of 34–5.

[57] Despite their successful qualifying campaign, expectations surrounding the Netherlands national team were comparatively low due to mixed pre-tournament friendly performances and the failure of the Dutch squad in Euro 2012, where they suffered three defeats out of three in the group stages in that tournament.

In their first group game at the World Cup, at the Estádio Fonte Nova in Salvador, however, Van Gaal's Dutch team came from behind to defeat reigning champions Spain 5–1.

[58] The Dutch victory over Spain was attributed in part to Van Gaal's use of counter-attacking tactics which disrupted the tiki-taka possession-based football of the Spanish team.

[84] Van Gaal lost his first competitive game in charge, a 2–1 home defeat to Swansea City in the opening match of the 2014–15 Premier League season.

[86] He won his first competitive game in United's fourth match of the league season, a 4–0 home victory over Queens Park Rangers, with goals from Di María, Herrera, Wayne Rooney and Juan Mata.

[96] United completed another sequence of seven league wins in a row between 28 February and 12 April, concluding with an impressive 4–2 defeat of champions and local rivals Manchester City.

[97] United were also knocked out at the quarter-final stage of the 2014–15 FA Cup by holders and eventual winners Arsenal, who inflicted a 2–1 home defeat on Van Gaal's team on 9 March.

[99] During the summer transfer window, Van Gaal strengthened his squad by bringing in Memphis Depay from PSV, Matteo Darmian from Torino, Sergio Romero from Sampdoria, Morgan Schneiderlin from Southampton, Bastian Schweinsteiger from Bayern Munich and Anthony Martial from Monaco.

Domestically, United were solid in defence and went top of the Premier League at the end of September; however, mixed results followed, leaving them in fourth position going into November.

[100] Fifteen days later, Van Gaal walked out of a press conference after being questioned about his future, amid speculations of dismissal following a six-game run without a win.

[102] After a 3–0 defeat away to Tottenham Hotspur on 10 April, several United players reportedly turned on Van Gaal in the dressing room, calling him "clueless" and questioning his tactics after he openly criticized young striker Marcus Rashford and several other players and made several questionable decisions during the match, a result which left United four points off fourth-placed Manchester City.

[114] Following their exit from the World Cup, Van Gaal resigned as head coach of the Netherlands national team, after 20 matches without defeat in his third stint.

[4][5][120][121] He served as an inspiration for several other coaches due to his teams' style of play and his use of a back–three defensive line, including Gian Piero Gasperini and Alberto Malesani, as well as influencing his former assistant José Mourinho, and his former players Pep Guardiola and Luis Enrique.

[128] In an interview with FIFA in January 2008, Van Gaal spoke of the importance of his football philosophy rather than the systems he used, as well as the need for flexibility as a coach, as demonstrated by his use of several formations throughout his career, such as the 4–3–3 and 3–3–1–3/3–4–3 with Ajax, the 2–3–2–3 at Barcelona, the 4–4–2 at AZ Alkmaar, and the 4–2–3–1 with Bayern Munich.

[143][145][146] Van Gaal also used a similar counter-attacking tactical approach during his third spell as head coach of the Netherlands at the 2022 World Cup, using a 3–4–1–2 formation, which divided critics.

[155] According to The Daily Telegraph, it emerged in 2009 that Van Gaal had lost millions of pounds investing in fraudster Bernie Madoff's Ponzi scheme.

In the advert, Van Gaal sends a team of Nike-sponsored players to retrieve a Nike Geo Merlin ball being held in a secure facility by robot ninjas.