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Tata Sons has four weeks to appeal the order given by the NCLAT, news agency Reuters reported quoting a lawyer involved in the case.
"For the Tata Group to prosper as an institution, it is important that the management of individual companies, their Boards, the management of Tata Sons, the Board of Tata Sons and the shareholders of Tata Sons, all work harmoniously within a robust governance framework, that in substance and form, protects the rights of all stakeholders," Mr Mistry said in a statement.
A two-judge panel of the NCLAT said on Wednesday that Tata Sons chairman emeritus Ratan Tata's actions against Mr Mistry were oppressive. The court also said Tata Sons' move to turn private was unlawful and ordered a reversal. Tata Sons' board had approved a plan to go private in September 2017.
Tata Sons, in a statement said, "The NCLAT order appears to even go beyond the specific reliefs sought by the Appellant. Tata Sons strongly believes in the strength of its case and will take appropriate legal recourse. Tata Sons assures its various stakeholders that it not only has always operated in a fair and equitable manner but also acted in accordance with the law and will continue to do so."
Mr Mistry launched legal proceedings against Tata Sons after his ouster from the company, one of the country's oldest and largest conglomerates.
In July last year, the National Company Law Tribunal (NCLT) dismissed Mr Mistry's plea challenging his removal as chairman of Tata Sons. The NCLT held that the Tata Sons board was competent to remove him as executive chairman and that he was ejected as the board members had lost confidence in him.
He appealed to the National Company Law Tribunal to overturn the dismissal and, following an unfavorable ruling, appealed to the NCLAT seeking to expunge disparaging remarks against him in the original order.
The Tata Sons board removed Mr Mistry as chairman and appointed Ratan Tata as interim chairman in October 2016. The change in the top management came about four years after he had taken over from Mr Tata.
In December 2016, Mr Mistry resigned as director from all Tata Sons companies and moved the NCLT alleging oppression of minority shareholders and mismanagement. In January 2017, Tata Sons named N Chandrashekaran as chairman. The next month, Mr Mistry was removed from the post of director on the Tata Sons board.
Mr Mistry currently serves as managing director of Shapoorji Pallonji & Company, which is part of the Shapoorji Pallonji group owned by his family. He joined the board of Tata Sons in 2006 and was appointed deputy chairman in November 2011.