The versatile forward moved to Monaco ahead of the 2012-13 campaign when the club were in the second tier of French football.
However, the Argentinian has found first-team football hard to come by at Stade Louis II this term and has started just seven times in the league.
Marseille have subsequently swooped to take the 20-year-old to the Stade Velodrome on a temporary basis, with Marcelo Bielsa's men retaining the option to make the deal permanent.
Ocampos could make his debut in Marseille's visit to Rennes on Saturday.
Marseille sit second in Ligue 1, just two points adrift of leaders Lyon.
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