Ben Arfa, 32, had been a free agent since leaving Rennes at the end of last season and has moved to Estadio Jose Zorrilla for the remainder of 2019-20.
A gifted attacking midfielder, Ben Arfa enjoyed good spells with Nice and Rennes either side of a frustrating period at Paris Saint-Germain from 2016 to 2018.
In 26 Ligue 1 appearances with Rennes last term, the France international – capped 15 times by his country – scored seven goals and set up another two.
A fine dribbler and creative force, Ben Arfa will be tasked with helping Valladolid avoid relegation, with Sergio's men 16th in LaLiga, five points clear of the bottom three.
Providing he proves his fitness, he could make his debut at Real Mallorca on Saturday.