Columnist and government critic Farhad Mazhar sparked a police hunt after leaving his Dhaka home on Monday morning.
There were reports of a ransom demand.
Police said Mr Mazhar, 69, was eventually found on a bus travelling to the capital from the south-western city of Khulna. It is unclear if he had been abducted.
Human rights groups say enforced disappearances and abductions are rising in Bangladesh.
Mr Mazhar is a supporter of the opposition Bangladesh Nationalist Party (BNP).
Party officials say many of their activists and supporters have been detained illegally since 2014.

Via a webpage visitors can control lights around windows, railings and doors as well as a Christmas tree in the house's garden.
The page is proving popular with hundreds of people every minute taking the chance to use the page to control the 11 different lights.
Live images of the light show are also being regularly uploaded to the web.
Ken and Rebecca-Ellen Woods of Fairbanks, Alaska started putting their lights online several years ago but this year the control system got a big upgrade.
Mr Woods, who works in IT, has built a dedicated computer-controlled switching box that has ports for every set of lights affixed to their home.
The live feed of the changing display shows lights blinking on and off at all times of day. Mr Woods told ABC News that he had got used to the constantly changing display. He added that it had got easier to live with once they only allowed lights on the exterior of the house to be controlled remotely.
There are no other houses near to the Woods household so there are no neighbours to complain about the flashing display.
This year the bill to run the hardware underpinning the light system looks set to reach more than $400 (Â£275) as millions of people take the chance to fiddle with the decorations over the Christmas period.
A well-known Bangladeshi human rights activist has been found on a bus after his family reported him missing.
[NEXT_CONCEPT]
An Alaskan family has added online controls to the Christmas lights adorning their home.