In between, he found time to author the Q-Report, detailing plans to professionalize the development of footballers in the United States.

[9] Queiroz was part of FIFA XI coaching staff, alongside Brazilian Carlos Alberto Parreira, in a humanitarian friendly match played in war-torn Sarajevo against Bosnia and Herzegovina on 25 April 2000.

[14] By mid-season, the team topped the La Liga table and was in contention for the Copa del Rey and the UEFA Champions League trophies.

They lost the Copa del Rey final to Real Zaragoza and were eliminated from the Champions League in the quarter-finals by Morientes's new team Monaco, after a 4–2 first leg win, ending the season with the Supercopa de España as the only trophy won, the first time in five years without a major trophy.

[17] In his 2014 autobiography, United captain Roy Keane stated that an argument with Queiroz about loyalty was one of the reasons why the Irishman quit the club in 2005.

For example, in 2008 Queiroz was – unsuccessfully – charged with improper conduct by the Football Association after describing referee Martin Atkinson's performance in a match as "a disgrace".

[21][22] In late March 2008, it was reported that Benfica had, once again, approached Queiroz to become their manager and had made a formal request to Manchester United.

[25] However, rumours over the summer of 2008 continued to link Queiroz with the Portugal national team managers' role, following the departure of Luiz Felipe Scolari.

[26] On 11 July 2008, Manchester United agreed to release Queiroz from his contract, and he was appointed manager for the Portugal national team.

On 11 July 2008, it was announced that Queiroz was leaving Manchester United, having agreed to a four-year contract to become the head coach of the Portugal national team.

Together with another goalless draw in Stockholm against Sweden, these results left Portugal with only six points out of a possible 15 and on the brink of missing a major international tournament for the first time since 1998.

This rout virtually guaranteed Portugal passage to the second round and a second goalless draw with Brazil confirmed qualification.

Quieroz was suspended for six months by the Portuguese Anti-Doping Authority (Autoridade Antidopagem de Portugal) on 30 August 2010, when he was judged to have disrupted their pre-World Cup procedures; he had been suspended for a month by the Portuguese Football Federation (FPF) for using inappropriate language towards the testers, a lesser charge that he admitted to.

[35][36] Iran, under Queiroz, began their World Cup qualification campaign successfully, defeating the Maldives 4–0 in the first leg of their second round of qualifiers.

Iran highlighted their position at the top of their group by defeating Bahrain 6–0 at home in the Azadi Stadium, as well as inviting former German youth international, Ashkan Dejagah, who scored twice on his debut against Qatar.

Team Melli then drew Qatar and lost in Lebanon before defeating South Korea at the Azadi on 16 October with a goal from captain Javad Nekounam.

[38] In the opening match of the tournament on 16 June, Iran drew Nigeria 0–0, making it their first clean sheet of the FIFA World Cup.

Having received a controversial red card in the first half from referee Ben Williams, Iran led a valiant effort with ten men, scoring two goals late in extra time to draw the match 3–3.

[49][50][51] Iran began their 2018 World Cup qualification campaign with friendly matches against Chile and Sweden in March 2015.

Iran finished top of the group with 20 points from eight games, Queiroz and his team managed to avoid defeat and remain unbeaten in the second round of World Cup qualifying.

Their final match saw Queiroz come up against his home country, Portugal; after going 1–0 down, goalkeeper Alireza Beiranvand saved a penalty from Cristiano Ronaldo to give Iran hope, but they had to wait until injury time at the end of the second half for an equaliser from Karim Ansarifard.

[59] On 23 September 2018, Queiroz extended his contract until the 2019 AFC Asian Cup,[60][61] hoping to win Iran's first continental title since 1976.

[67][68] However, when matches resumed following the COVID-19 pandemic, Colombia's performance slipped disastrously, with a 0–3 home loss to Uruguay (its worst ever home loss in 82 years) before being shockingly thrashed 1–6 by Ecuador, the biggest ever defeat, and this finally put the end to Carlos Queiroz's reign as Colombia's boss.

[69][70] On 8 September 2021, the Egyptian Football Association announced the signing of Carlos Queiroz to replace Hossam El Badry.

[74] The Egyptian national team qualified for the quarter-finals by penalty shootout, after defeating Ivory Coast 5–4 in the round of 16.

[77] This win marked for the first-time ever Queiroz had guided a national team into the final of a competitive football tournament.

However, after a 1–0 win in Cairo, and a 1–0 loss in Dakar, Egypt lost again on penalties; hence, they failed to reach the final competition.

His appointment was promised as part of Mehdi Taj's successful campaign for a second spell as president of the Football Federation Islamic Republic of Iran.

[85] Queiroz was appointed manager of the Qatar national team in February 2023, succeeding Félix Sánchez, who led them at the 2022 FIFA World Cup which they hosted.

[86] On 6 December 2023, after twelve matches with Queiroz charge, consisting of four victories, three draws and four losses,[87] the Qatar Football Association announced that his contract had been terminated by mutual agreement,[88] and he had been replaced by Tintín Márquez.