He spent most of his professional career with Barcelona in La Liga appearing in 535 official games whilst winning 21 major titles.

In 2012, Valdés made a goalkeeping error against Real Madrid in the Supercopa de España that culminated in Ángel Di María scoring a decisive goal and narrowing down Barcelona's two-goal advantage.

On 1 May 2013, in a 3–0 Champions League semi-final loss to Bayern Munich at Camp Nou, Valdés made his 100th appearance in the competition, becoming the 17th player to do so.

[14] On 23 October 2014, Manchester United offered Valdés the chance to complete his rehabilitation from a knee injury and to work his way back to fitness with the club.

[17] As part of a compensation package for reneging on their deal with Valdés, Monaco agreed to pay the difference between the £150,000 weekly wage he stood to earn with them and the lower salary offered by Manchester United.

[19] He made his first-team debut on 17 May against Arsenal at Old Trafford, replacing the injured De Gea for the final 16 minutes and conceding an own goal by Tyler Blackett for a 1–1 draw.

[20] A week later he made his first start for the team in their last game of the season away to Hull City, keeping a clean sheet in a goalless draw which relegated the opponents.

[21] On 15 July 2015, Manchester United manager Louis van Gaal announced that Valdés had been placed on the transfer list after it was claimed he had refused to play in a reserve game.

[26][27][28] On 23 January 2016, Manchester United announced that Valdés would be moving to Belgian club Standard Liège on a six-month loan deal.

[31] His loan spell was cut short on 29 April after the club decided to allow more youth players the opportunity to play in games at the end of the season.

[32] On 7 July 2016, Valdés signed a two-year deal on a free transfer at recently promoted Middlesbrough, managed by compatriot Aitor Karanka.

[43] After being overlooked by various coaches of the Spanish national side for several years,[44][45] on 20 May 2010, he was included by Vicente del Bosque in Spain's final 23-man squad for the 2010 FIFA World Cup in South Africa as the third-choice goalkeeper behind captain Iker Casillas and Pepe Reina wearing the number 12 shirt.

[46] On 3 June 2010, Valdés earned his first cap, starting in a friendly match between Spain and South Korea at Tivoli-Neu in Innsbruck, Austria.

[51][52] His sole appearance in a major tournament came in their last group game, keeping a clean sheet in a 3–0 win over Nigeria at the Estádio Castelão in Fortaleza.

[53] Valdés was considered fiercely competitive and demanding, demonstrating great mental strength and concentration to be alert during long spells of ball domination, and was superb at one-on-ones.

[55][56][59][60] On 1 June 2018, Valdés returned to football as a manager by acquiring his UEFA Pro Licence alongside compatriots such as Xavi, Raúl and Xabi Alonso.