Naveed Akram opened fire on a crowd of people celebrating Hanukkah at Bondi Beach alongside his father, 50-year-old Sajid Akram, on December 14.
The attack left 15 people dead - including a 10-year-old girl - and dozens more injured.
The elder Akram was shot dead by police, while his son was charged with 59 offences and held at Goulburn's supermax prison.
The existing charges included committing a terrorist act, 15 counts of murder, and 40 charges of attempted murder over his alleged role in the massacre.Â
But the 24-year-old has been hit with a further 19 charges while in custody, including 10 counts of shooting with intent to murder and six counts of discharging a firearm with intent to resist arrest.
According to records, the additional charges were added to the court file in April - ahead of a mention of the matter in Sydney's Downing Centre Local Court on Wednesday.
He has not yet been required to enter pleas to any of the charges.
The father-and-son attack was Australia's deadliest mass shooting since the Port Arthur massacre in 1996.
The men allegedly tossed three pipe bombs filled with steel ball bearings and a tennis ball bomb into a crowd celebrating Hanukkah at Archer Park before opening fire.
None of the bombs detonated.
A box-like bomb was also allegedly found in the boot of their car while two hand-painted ISIS flags were also in the vehicle.
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