People, many in tears, gathered around a makeshift shrine of flowers and candles at the foot of the enormous Christmas tree at Kleber Square in the city centre.
The ceremony, organised by local rights associations with the approval of the city authorities, included music, singing and several readings.
The traditional minute of silence was replaced by a minute of noise, during which people shouted and applauded to express their solidarity with the victims.
Earlier on Sunday, police in the eastern French city, which is home to the European Parliament, released two close associates of the attacker, Cherif Chekatt who was on a French list of possible extremist security risks.
With the release Saturday of Chakett's parents and two of his brothers, that leaves only one person of the seven originally detained still in custody.
Chekatt was shot dead by police on Thursday after a manhunt that involved more than 700 members of the security forces.
The 29-year-old native of the city attacked Strasbourg's Christmas market on Tuesday armed with a gun and a knife, killing four and wounding 11 others.
Police have been focusing their investigation on whether Chekatt had any help in carrying out his attack or during the two days he was on the run.
France's interior minister on Friday dismissed a claim by the Islamic State group that it was responsible for the attack