During a UEFA Euro 2020 match on 12 June 2021, Eriksen collapsed on the pitch after suffering a cardiac arrest; he was given cardiopulmonary resuscitation and was later fitted with an implantable cardioverter-defibrillator.

Eriksen made his senior international debut for Denmark in 2010 at age 18, and has since earned 140 caps, including appearing in six major tournaments; he was also the youngest player at the 2010 FIFA World Cup.

[6] Eriksen ultimately underwent trials with both clubs as well as Real Madrid, Manchester United and Milan, but finally decided to move to Ajax, stating, "My first step should not be too big.

[15][16] Eriksen's form throughout the campaign earned praise from manager Martin Jol who compared him to former youth products Wesley Sneijder and Rafael van der Vaart as well as Danish legend, Michael Laudrup for his reading of the game in the traditional number 10 role.

[10] Eriksen took the number eight jersey ahead of the following campaign and began the 2010–11 season well, scoring his first Ajax league goal on 29 August 2010 in an away victory over De Graafschap.

[24] In the return fixture the following month, he provided assists to teammates Gregory van der Wiel and Siem de Jong as Ajax recorded a 4–0 victory.

[25] Five days later he was named Danish Football Player of the Year in recognition of his role in helping Ajax to the league title the season before and in Denmark's successful UEFA Euro 2012 qualification campaign.

[26] Eriksen continued to impress for Ajax and his strong contribution, both in terms of goal and assist returns, helped the club to a second consecutive league title.

[31] After the match, Spurs manager André Villas-Boas commented, "It was a great debut for Christian, he is a pure number 10, a creative player and his individual quality made all the difference.

"[32] Five days later, Eriksen "clipped a wonderful dipping shot" over the goalkeeper to score his first Tottenham goal and complete a 3–0 win over Tromsø IL in the Europa League.

[37][38] Ahead of the 2014–15 campaign, Tottenham appointed Mauricio Pochettino as new club manager after the unsuccessful period under Villas-Boas and interim-manager Tim Sherwood.

[43] Eriksen completed the 2014–15 campaign having featured in every Premier League game for Mauricio Pochettino, starting all-but one match, and scored 12 goals across all competitions.

Following the match, teammate Harry Kane, who was challenging for the season's Golden Boot award, claimed to have made the last touch on the ball for the second goal.

[67] On 28 January 2020, with his contract at Tottenham set to expire in six months, Eriksen signed a four-and-a-half-year deal with Serie A club Inter Milan that would earn him €10 million per season.

[68] He made his club debut the following day, coming on as a second-half substitute for Alexis Sánchez in 2–1 home win over Fiorentina in the Coppa Italia quarter-finals.

[79] Close to half a year after his cardiac arrest, Eriksen began individual training at the facilities of his youth academy team OB in Odense in preparation for a possible comeback to football.

[82] On 26 February 2022, his first appearance was as a substitute in a 2–0 defeat to Newcastle United - he replaced Mathias Jensen, who came on in Eriksen's place in the game in which he suffered a cardiac arrest.

[85] Between the date of Eriksen's Brentford debut and the end of the season, only Kevin De Bruyne and Martin Ødegaard created more chances in the Premier League.

[101] On 28 May 2010, Denmark coach Morten Olsen announced that Eriksen would be part of the final squad of 23 participating in the 2010 FIFA World Cup in South Africa.

Eriksen played a key-role during the nation's qualification campaign during which time he scored eight goals to earn Denmark a play-off against the Republic of Ireland.

[111] The first leg of the play-off ended in a 0–0 home draw before Eriksen netted a hat-trick in Dublin's Aviva Stadium in a 5–1 win to earn Denmark a spot at the World Cup.

[118] On 12 June, while playing in Denmark's opening group stage match against Finland at Parken Stadium in Copenhagen, Eriksen collapsed in the 42nd minute as he was about to receive a throw-in.

[120] Urgent medical assistance arrived immediately, and cardiopulmonary resuscitation and defibrillation were performed on the field before Eriksen was taken off the pitch on a stretcher and the match was suspended.

[121][122] Around an hour after the incident, UEFA and Danish Football Association (DBU) officials confirmed from the Rigshospitalet Hospital that Eriksen had been stabilized and was awake.

[127] Denmark manager Kasper Hjulmand and team doctor Morten Boesen both later expressed regret at the match's continuation,[128] although Eriksen's teammate Martin Braithwaite said that the decision to do so was the "least bad one".

[136] The operation jeopardised his contract with Inter Milan due to Serie A rules, which did not allow players wearing ICD devices to play.

[144] In the last group stage encounter against Serbia, he featured in his 133rd international match, becoming the most-capped Danish player ahead of his teammate Simon Kjær.

[148] Possessing significant vision, passing range, crossing accuracy, set-piece delivery, creativity, technical skills, movement, and an ability to read the game, as well as good balance and co-ordination, Eriksen is highly regarded by pundits for his ability to orchestrate attacking moves for his team with his distribution, create or exploit spaces with his runs, and provide assists to his teammates; his range of skills make him an effective playmaker and creator of chances.

[10][146][147][148][149][150] He is also known for his eye for goal from midfield, and for his ability to strike the ball with power and accuracy with either foot, despite being naturally right-footed, in particular from distance;[148][149][150] moreover, he has also established himself as a free kick specialist.

[5][151][152] Due to his playing style, nationality, and role, pundits have compared him to his compatriots Michael and Brian Laudrup,[10][23] who were two of his major influences in his youth, as well as Wesley Sneijder and Rafael van der Vaart;[10][146] Eriksen has also cited Francesco Totti as an inspiration.