Clos replaces Briton Adrian Quaife-Hobbs, who announced on Wednesday that he was switching from MP to Hilmer Motorsport in place of Robin Frijns.
"We're delighted to welcome Dani to the team," said MP team principal Sander Dorsman.
"The experience he brings to the team will be priceless. He's won in GP2 and has tested in Formula 1. We're all really looking forward to working with him for the first time in Hungary this weekend."
Clos, 24, competed in GP2 from 2009-12, winning at Istanbul Park in '10 and adding an Asia Series success at Imola in '11.
He was the Italian Formula Renault champion in 2006 and was a podium finisher in both the F3 Euro Series and FR3.5.
He spent last year as the test driver for the HRT F1 team, taking part in four Friday practice sessions. He has also tested for Williams.
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