Copil began to gain experience on the Future Tour in 2005. In August 2007 he won his first future tournament in his home country when he beat the Argentinian Martín Alund 6: 3, 6: 4 in the final. His first Challenger tournament , the second highest tournament category, he played in September 2007 in Brașov . There he failed in the first round against his compatriot Adrian Ungur . Until 2009, Copil tried unsuccessfully to qualify in tournaments on the ATP World Tour . After attempts in Bucharest , Halle and 's-Hertogenbosch , he got his first match in the main round of a World Tour tournament in Bucharest in September thanks to a wildcard . There he defeated Victor Crivoi 6: 3, 6: 2 at the beginning , then lost to Rubén Ramírez Hidalgo 3: 6, 7: 6, 4: 6 in the second round .
On September 18, 2009 he made his debut for the Romanian Davis Cup team . On hard court he benefited from the surrender of his Swedish opponent Andreas Vinciguerra with a score of 6: 4 .
In early 2010, Copil won his third Future tournament in Guatemala. In May of that year he made his first place in the final at Challenger level in Cremona as a qualifier , where he was defeated by Denis Gremelmayr 4-6, 5-7. In Bucharest , Copil played again in 2010 thanks to a wildcard and lost to Simone Vagnozzi 6-7 , 4-6. In Kazan , the Romanian finally managed to win his first challenger title against Andreas Beck . In May he played for the first time in the qualification of a Grand Slam tournament at the French Open . There he reached the second qualifying round.
In 2018 he reached the final in Basel and was defeated there by Roger Federer 7: 6, 6: 4. Getting into the final of this ATP World Tour 500 tournament is the greatest success of his career.