Those on trial include seven crew members, five staff from Cyprus-based Louis Hellenic Cruises (LHC) that owned the vessel and an employee of risk assessment organisation DNV that had deemed it seaworthy.
The trial is expected to last over a month as over 60 witnesses are to testify, state news agency ANA said.
The defendants face misdemeanour charges including endangering sea transport and causing death and environmental pollution through negligence.
The Sea Diamond sank near the Aegean island of Santorini in April 2007 after hitting a reef.
Two French passengers a man and his daughter -- were never found and are assumed dead, but some 1,600 other passengers and the crew were evacuated safely.
The ship sank to a depth of 140 metres (450 feet) with much of its fuel still on board, raising fears of lasting environmental damage.
But the government said that at least two-thirds of the 400 tonnes of fuel onboard was pumped out of the ship after the incident, eliminating any major pollution risks.
Its owners paid for a surface clean-up operation but refused to remove the ship because of the depth, warning that the wreck could fall apart and spill the remaining fuel over a wider area.