"At 24 I feel my best years are still to come. But for this stage of my life and with an eye to the future, I have to set myself and my future family up so they can have every opportunity in life to succeed."
Chiefs head coach Dave Rennie said: "James has made a massive contribution to the Chiefs over the past four seasons.
"His unique skillset, leadership and attacking mindset makes him one of the best left wingers in the world. It is a smart signing by Leinster. James is a top man, great in the community and has been a pleasure to work with."
Lowe made his Super Rugby debut for the Chiefs against the Crusaders in 2014. Renowned for his powerful left boot and evasive attacking style, Lowe has scored 18 tries in his 39 appearances for the Chiefs.
The Maori All Blacks representative showed his resilience as a teenager after being diagnosed with Juvenile Rheumatoid Arthritis, a condition that left him bedridden. The affliction did not stop Lowe from realising his childhood dream of becoming a professional rugby player and he now works as an ambassador for Arthritis New Zealand to inspire young Kiwis to achieve their goals.