Of the 24 people convicted for the so-called Gulbarg Society killings, 12 were jailed for seven years while one man was sentenced to 10 years.
During the attack, 69 people were hacked and burned to death by a mob.
More than 1,000 people, mostly Muslims, died in the riots, sparked by a fire on a train that killed 60 Hindu pilgrims.
Critics of Prime Minister Narendra Modi, who was the state chief minister at the time, say he did little to stop the riots.
The special court in Ahmedabad called the incident the "darkest day in the history of civil society".
However, Zakia Jafri, the wife of Ehsan Jafri, a prominent Muslim politician and a former Congress party MP, who was among those killed, has expressed disappointment at the sentencing.
"I was there when Ehsaan Jafri was killed, it's not justice at all," she told reporters.
Survivors of the Gulbarg massacre say he fired his gun in self-defence as the mob attacked the complex.
Mrs Jafri says her husband called Mr Modi for help but it never came.