Born in Trikkalangode village in Malappuram, Arjun spent his formative years at the MSP Football Academy and in the 2012 Subroto Cup, he was adjudged Best Player of the tournament. He also represented the Calicut University team which went on to win the All-India Championship.
Jayaraj was part of the FC Pune City Reserves side when newly-founded Gokulam Kerala came calling for him in 2017. Playing for Calicut University against Gokulam in a friendly, the attacking midfielder impressed coach Bino George and was signed shortly thereafter.
In two seasons with the Malabarians, Arjun has helped them win the Kerala Premier League in 2017-18 and in the I-League, he took over the attacking midfield role from the outgoing Bahraini player Mahmood Al-Ajmi. Overall, he has made 30 appearances and scored twice in the I-League.
Kerala Blasters have been signing players originating from the state of Kerala this transfer window. Arjun Jayaraj follows TP Rehenesh, Shibinraj Kunniyil and Rahul KP who all joined the club this season.