Born in Valencia, Soler joined hometown club Valencia CF's youth setup in 2005 at the age of eight after impressing them while playing for Bonrepòs, the team of his neighbourhood. Initially a prolific striker, he was pushed back to an attacking midfielder and to central midfielder during his graduation at Valencia He made his senior debut with the reserves on 3 May 2015, starting in a 0–1 Segunda División B away loss against UE Cornellà. Soler scored his first senior goal on 13 December 2015, netting his team's second in a 2–2 draw at CF Badalona. The following 12 March he renewed his contract, and was an unused substitute in the main squad's 2–1 home win against Athletic Bilbao for the season's UEFA Europa League. On 10 December 2016 Soler made his first team – and La Liga – debut, replacing Mario Suárez in a 2–3 loss against Real Sociedad at the Anoeta Stadium. He scored his first goal in the category the following 21 January, netting the first in a 2–0 Valencian Community derby win against Villarreal CF at the Estadio de la Cerámica. Aged 22 years, two months and five days, Carlos Soler became the ninth-youngest player in Valencia CF's history to bring up his century of appearances for the club. Soler had gradually established himself in the first-team picture before becoming a key cog in Los Che's midfield. Indeed, the academy-reared starlet ended the 2018/19 campaign top of the Valencians' appearance charts after featuring 63 times across all competitions. That season, which marked the club's centenary year, culminated in trophy success as Valencia lifted the Copa del Rey, whilst Soler struck the opening goal in the game that saw the team clinch qualification for the 2019/20 Champions League. In the previous edition of Europe's elite club competition, the Valencia-born youngster provided the joint-highest number of assists, along with Manchester City's Riyad Mahrez. In addition, Soler had a hand in each of the six goals that his side scored in the competition, with his impressive performances securing him a spot in the team of the group stage. In 2019, and after having tasted Copa de Rey glory with Valencia, he capped off a season that really saw him make his breakthrough by claiming a winners' medal with Spain at the Under-21 European Championship. Soler had played an instrumental role in La Rojita's qualifying campaign, during which he clocked up the most game time across the squad. On 17 December 2019, Soler signed a four-year contract extension, keeping him at the club until 2023, with his release clause was set at €150 million.
