Former Barca forward Valverde announced last week that he was leaving Athletic Bibao after four years in charge.
He replaces Luis Enrique, who revealed in March that he would leave the club – who finished second in La Liga – at the end of his three-year contract.
Enrique led Barcelona to the treble in his first season, the domestic double in 2016 and the Copa del Rey this year.
They beat Alaves 3-1 in Sunday’s final – his last match in charge.
Barca president Josep Maria Bartomeu praised 53-year-old Valverde’s “ability, judgement, knowledge and experience”, adding: “He promotes young players and he plays the Barca way.”
Valverde’s presentation as Barca’s new coach will take place on Thursday.
Andy West, BBC Spanish football writer
In many ways, Ernesto Valverde’s appointment at Barcelona makes perfect sense.
His task is to instil a convincing collective structure into a team too often over-reliant on Lionel Messi recently, and especially to address the defensive vulnerabilities which saw Barca concede 10 goals in this season’s Champions League trips to Juventus, PSG and Manchester City.
And Valverde has the credentials to be successful. He is an experienced and intelligent coach with good organisational and communication skills, implementing a fast-paced style of play which earned the regular approval of the most important figure in the club’s history, his former manager Johan Cruyff.
Despite those plus points, however, Valverde will receive little more than a lukewarm welcome from many fans, who are sceptical of his abilities to master the internal politics inherent at such a huge club.
There are fears that his understated personality will see him become a ‘yes man’ to an increasingly unpopular board of directors, lacking the strength of character to reinvigorate a team who have been treading water for too long.
When Luis Enrique announced his decision to resign, a poll over the identity of the new coach by newspaper Mundo Deportivo saw Valverde receive just 8.4% of the votes (Jorge Sampaoli came first), so it’s clear his arrival is not being universally acclaimed.
It doesn’t help that his final season in Bilbao yielded a pretty disappointing seventh-place finish and an embarrassing Euorpa League exit against Cypriot minnows Apoel Nicosia.
If he doesn’t make a good start, patience will be in short supply.
Valverde, who was born in the Spanish region of Extremadura but raised in the Basque Country, started his playing career as a forward with local sides Alaves and Sestao, before spending two years with Espanyol.
He joined Barcelona in 1988, at the age of 24, and scored eight goals in 22 matches in two injury-hit seasons with the club.
From there he went to Athletic Bilbao, the club his career is most strongly linked with, scoring 44 goals in 170 matches over six years. He ended his playing career with one season at Mallorca. He was capped once for Spain, playing 19 minutes at the end of a Euro 92 qualifier against Iceland.
Immediately after his 1997 retirement, he moved back to Athletic as a youth-team coach, eventually becoming first-team boss in the 2003-04 season. After leading them to fifth and ninth place in two seasons in charge, he left the club.
A year later he took over Espanyol and led them to the Uefa Cup final in his first of two seasons as manager.
He then went to Olympiakos, leading them to a Greek league and cup double, before leaving for a year at Valencia.
Valverde went back to Olympiakos for another two seasons, winning the league twice and the cup once before leaving again.
After returning to Athletic in 2013, he said: “Sequels are never any good. Well, the Godfather II was quite good.”
In his first season back at the club – who can only sign players with links to the Basque region – he led them to fourth place in La Liga and a Champions League spot.
There were top-seven finishes for the next three seasons, including seventh this term, and a run to the 2014-15 Copa del Rey final. They beat Barcelona 5-1 on aggregate in the 2015 Spanish Super Cup.
Barcelona have not brought through many youngsters in recent years. Rafinha and Sergi Roberto are the only two youth products younger than 28 who are regulars in the squad.
But Valverde – who has favoured a 4-2-3-1 formation – has plenty of experience giving young players a chance. As Athletic cannot buy non-Basque players, he often had to look to his youth team for players.
Defender Aymeric Laporte and winger Inaki Williams, who have both been linked with big-money moves to English clubs, became first-team regulars under Valverde. Right-back Inigo Lekue has been named in the Spain squad since his 2015 debut.
Valverde will also try to bring some defensive solidity to the club – he has often balanced defence and attack well. In 2009, Olympiakos conceded only 14 league goals on their way to the Greek title. Athletic never conceded more than 45 goals in a La Liga season during his second spell in charge.
Earlier this week, after Valverde left Athletic, and it was widely expected he would join Barcelona, Barca defender Gerard Pique said: “Ernesto has done a great job at Athletic the past few years. He played here for Barcelona as a player and I think he could be a good option, as could others.”
During the season, Williams said: “He would be a good coach [for Barca], but we want him to remain at Athletic. He’s brilliant, a great coach.
“He’s done a great job. He’s made history at the club – he’s the coach with the most games. He has the final word and whatever happens I will be pleased for him.”
Valverde is not your typical football manager.
While playing for Barcelona, he studied photography at the Institut d’Estudis Fotografics de Catalunya. In 2012, he released a book of artistic black and white pictures, called Medio Tiempo, which translates as Half-Time.
He also ran an exhibition of his pictures that summer in Greece, where he was managing Olympiakos.
“These are photographs that show a world that is not a home, neither a house or a country, with spaces such as hotels, planes, buses, football fields, touristic areas and, in general, lonely places or places where anyone could have that feeling. So lonely seem to be the people portrayed by him,” read Bernardo Atxaga’s prologue to the book.
Johan Cruyff writing in La Vanguardia newspaper, January 2007, while Valverde was managing Espanyol.
“His players might play well or not, sometimes they win and other times they don’t, but they always go onto the pitch with a dream. Valverde always gives fans reasons to be proud of their team.”
Lionel Messi in Facebook: “Wishing you the best of luck in the next stage of your life, Luis Enrique. Thank you for everything in the last few years.”