Yes, FILLETS is a Scrabble word!

Letter values in Scrabble US: F 4, I 1, L 1, L 1, E 1, T 1, S 1.

Is it a valid word?

FILLETS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a boneless steak cut from the tenderloin of beef
a longitudinal slice or boned side of a fish
a bundle of sensory nerve fibers going to the thalamus
a narrow headband or strip of ribbon worn as a headband
fastener consisting of a narrow strip of welded metal used to join steel members

Also: fish fillet, fish filet.