Caesar Holloway, 34, was already in police custody when he was charged in the killings of 34-year-old Rian Thal and 40-year-old Timothy Gilmore.
It was not immediately clear what he was being held for.
Thal and Gilmore were shot in the city's Northern Liberties neighborhood in what police say was a drug robbery.
Investigators seized four kilograms of cocaine and more than $100,000 from Thal's apartment following the shooting.
Holloway is being held without bail on charges including murder, robbery and conspiracy.
A total of seven people have now been charged in this case.
