On 27 August 2017, Nakajima moved abroad for the first time, signing a season-long loan with Portimonense of Portugal's Primeira Liga.

[4] In February 2019, Nakajima joined Qatar Stars League side Al Duhail[5] for a reported transfer fee of €35 million.

[8][9] Nakajima made his Porto debut on 13 August 2019 in the second leg of the UEFA Champions League third qualifying round away to Krasnodar, playing the full 90 minutes of a 3–2 loss that eliminated the team on the away goals rule.

[11] On 16 January 2021, Nakajima joined Al Ain of the UAE Pro League on a six-month loan deal including an optional €40 million transfer clause.

He made his debut on 18 September 2022 against Adana Demirspor, coming on the 59th minute only to be sent off in just 20 seconds after receiving a red card for a late sliding tackle.

In January 2016, he participated in the championship, scoring a double in the extra-time of the quarter-finals match against Iraq[31] and eventually won the competition with a 3–2 triumph against South Korea.

[38] Hajime Moriyasu named Nakajima in the squad for the 2019 Copa América in Brazil, which Japan guest entered with a mainly under-23 team.