The 30-year-old Diarra, who won a string of honours with Lyon and then Real, left relegated Monaco last year after a short spell with the French outfit and heads to Fulham on a free transfer until the end of the season, with the option of a further year.
The Mali international had four-and-a-half years in Madrid, lifting two league titles and a Spanish Cup having arrived in 2006 for a reported 30 million euros from Lyon, where he won four championships in as many years.
Diarra began his career with Greek side OFI Crete.
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