MPH Bookstores will be closing its two remaining outlets at Raffles City and Parkway Parade on July 28 and Sept 1 respectively.
It has begun clearing stock to prepare for the last day of operations.
The company told The New Paper on Wednesday that it was exploring potential locations to relocate to a single outlet.
It declined to name likely locations because of negotiations.
MPH cited the unsustainable high rental costs of both outlets and intense competition with major e-commerce players in Singapore as reasons for the closures.
The company said it was restructuring and streamlining resources for new business initiatives, and it was confident that bookstores will continue to be relevant.
It noted that bookstore chains in Britain had overcome challenges to turn their business around.
When TNP visited MPH's Parkway Parade outlet on Tuesday, the shelves were still filled with books, with boxes at the back the only indication of the move.
At the larger Raffles City outlet, however, most shelves had been cleared.
MPH's closures come after Japanese chain Books Kinokuniya shuttered its Liang Court outlet on April 21.
Then, on June 23, local chain Popular closed its Thomson Plaza outlet after 31 years there. Popular said the closure was due to lease issues.
MPH's closures mean more bad news for the local book industry, Epigram Books founder and publisher Edmund Wee said.
"Fewer outlets mean fewer places for publishers to sell books and fewer places for readers to buy books," he told TNP.
"Writers will continue to write, so publishers will just have to get creative on how to sell the books."
MPH's Raffles City outlet is having a moving-out sale until July 28, with 30 per cent off storewide and 50 per cent off selected items.
The Parkway Parade outlet will have its moving-out sale next month.
This article was first published in The New Paper. Permission required for reproduction.