In a video posted online, Les Miserables actor Eddie, 32, can be seen nominating Jamie before pouring a freezing bucket of ice water over himself.
Jamie, 32, lends a helping hand, chucking a second bucket over his friend, before stepping up for the challenge himself.
Nominating Spiderman actor Andrew Garfield, the Northern Irish star then quickly empties a bucket over himself – while Eddie gets his revenge.
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Eddie Redmayne and Jamie Dornan prepare to complete the Ice Bucket Challenge
Jamie's participation in the ALS viral campaign came hours after the handsome Fifty Shades of Grey star joined Instagram.
To the delight of his many female fans, the star’s first photo was a selfie, in which Jamie poses with a sign that reads, "I am Spartacus" with the 'Spartacus' crossed out and replaced with "Jamie Dornan" and a kiss.