Governor V Shanmuganathan administered the oath of office to the Chief Justice at a ceremony in Raj Bhavan where Chief Minister Mukul Sangma and his cabinet colleagues, judges and government officials were present.
Maheshwari replaces former chief Justice Uma Nath Singh who retired on January 14.
Maheswari was earlier a senior Judge of the Allahabad High Court.
After Justice Singh's retirement, Justice T N K Singh took over as acting chief justice till his retirement last month.
Since then, the Meghalaya High Court has been functioning with only one Judge, Justice S R Sen who was also serving as the acting Chief of the high court.