The streaming service will screen all the eight movies for a month without any charge to the new subscribers, Entertainment Weekly reported.
The development comes after the basic cable rights to exhibit the movies were earned by NBCUniversal (from Disney) last August. This was to be followed up with plans to screen the movies on Syfy and USA later this year.
HBO and Warner Bros, the studio behind the franchise, are both owned by Time Warner Cable.
The franchise based on J K Rowling's bestseller eight- part book series on the boy wizard, the first movie, "Harry Potter and the Sorcerer's Stone" released in 2001.
It also led to a spin-off, "Fantastic Beasts and Where to Find Them", which released last year, with its sequel, starring Johnny Depp, Eddie Redmayne and Jude Law, to be released on November 16.