Eiji Kawashima was born on 20 March 1983 in Yono, Saitama. After graduating from Urawa Higashi High School, he signed with Omiya Ardija in 2001, then played for Nagoya Grampus before joining Kawasaki Frontale in 2007, where he established himself as one of the J1 League's premier goalkeepers and won the AFC Asian Cup with Japan in 2011.
In summer 2010 Kawashima made the unusual move of heading to Belgium with Lierse, becoming one of the first Japanese goalkeepers to play regularly in a European top division. He then joined Standard Liège in 2012, where he was part of three Belgian Cup–winning sides. Spells at Dundee United in Scotland and Metz in France followed, before he joined Strasbourg in summer 2018 — a move that proved highly successful. With Strasbourg he won the Coupe de la Ligue in 2018–19, the club's first major trophy in 14 years, and remained on their books until 2022, including occasional Strasbourg II appearances in National 3 to keep match-fit.
In 2024 Kawashima returned to Japan with Júbilo Iwata at the age of 41. He started 32 J1 League matches in 2024 and continued playing in 2025 in the J2 League after Júbilo's relegation — astonishing longevity for a goalkeeper.
For Japan, Kawashima has appeared at four FIFA World Cups (2010, 2014, 2018, 2022) — a Japan record for any player at the time. He won the 2011 AFC Asian Cup, multiple Kirin Cups, and remains one of the most respected senior figures in Japanese football. Even into his 40s, he continues to feature in Japan training camps as the senior leader of the goalkeeping group.