The money will be used to pay back existing debt, but the move is seen as a sign of confidence in the business, which was created in a takeover of mobile operator SFR by cable company Numericable in 2014. Altice, the owner, is controlled by businessman Patrick Drahi.
The company began last week planning to raise $2.25 billion, and then increased it to $3 billion and finally $5.2 billion within a few days.
According to market experts, the previous largest such deal was a loan of $4.25 billion to Sprint in September 2013.
Reuters quoted one unnamed investor as saying that the Numericable-SFR was three times oversubscribed, meaning that the company was offered a total of $15 billion.
The deal means Numericable-SFR has no significant debt repayments due for the next six years.
