The twins are accused of helping three others beat a man outside a Phoenix recreation centre on Jan. 24. The brothers entered their pleas Thursday morning in Maricopa County Superior Court.
According to a Phoenix police report, 36-year-old Erik Hood says five people, including the Morris brothers, repeatedly punched and kicked him. Hood says he suffered a fractured nose, abrasions and a large bump on his head.
A call to the Suns for comment on the case was not immediately returned.
The six-foot-nine twins became teammates in 2013 when Marcus was traded to the Suns.
Their next court appearance is an initial pretrial conference set for June 30.