The suspects face life sentences if convicted of charges ranging from using violence to try to overthrow the government and parliament, to killing nearly 250 people.
Turkey blames the July 15, 2016 coup attempt on Muslim cleric Fethullah Gulen, a claim he strongly denies.
Gulen, who lives in self-imposed exile in the United States, is among several of the 221 suspects named in the indictment but are on the run, with the rest set to appear in court.
The attempted coup left 249 people dead, not counting 24 coup-plotters killed on the night of the putsch attempt.
Also among the suspects in one of Turkey’s highest-profile prosecutions are several high-ranking military officers including ex-air force commander Akin Ozturk.
Several of those on trial are accused of leading the so-called “Peace At Home Council,” the name the plotters are said to have given themselves the night of the failed overthrow.
The case is being heard in Sincan near the capital Ankara, at a facility that was purpose-built to hear coup-related trials.
In the opening trial in May, alleged coup plotters were booed by protesters as they entered the courtroom, with some shouting slogans in favor of “death penalty” for the suspects.
The trial is one of many being held across the country to judge the coup suspects in what is the biggest legal process of Turkey’s modern history.
The government has launched a massive crackdown under state of emergency laws imposed in the wake of the failed coup which have been extended several times.
Over 140,000 people, including public sector employees, have been sacked or suspended over alleged links to the coup while 50,000 people have been arrested since July 2016.
This week will also see other hearings in Istanbul including journalists from opposition Cumhuriyet newspaper who are standing trial on charges of aiding and abetting terrorist organizations.
One of Turkey’s acclaimed authors Asli Erdogan will appear before a court Tuesday on charges of spreading terror propaganda on account of her links to a pro-Kurdish newspaper.
In December she was released pending trial, after 132 days of pre-trial detention.
Last week, an Istanbul court ordered the release on judicial control of eight human rights activists including Amnesty International’s Turkey director Idil Eser, as well as a German and a Swede.
The cases involving journalists have received criticism from human rights advocates who claim the government is seeking to stifle dissent.