Cyclone Sidr hit the impoverished South Asian country on Nov. 15 with winds of 250 kph (155 mph) and a 5-metre storm (17-foot) surge, killing more than 3,300 people.
"... an alarming assessment has shown that more than one million storm survivors remain in need of basic, preliminary shelter assistance," said the International Federation of Red Cross and Red Crescent Societies in a statement.
"This finding is the result of a comparison between the extent of Sidr's damage and existing commitments from the international community to address shelter needs," the Red Cross said on Friday in the middle of the Muslim Eid holiday.
According to government figures, more than 1.5 million houses were fully or partially damaged by Sidr, the deadliest storm since 1991 when a cyclone killed about 143,000 Bangladeshis.
"The resilience and rapid rebuilding capacity of communities has been impressive," said Graham Saunders, head of the federation's shelter department in Geneva.
"And the efforts of the humanitarian community have also averted a major public health crisis and the ensuing loss of life that so often follows such disasters."
The assessment comes from more than 30 agencies involved in supporting survivors to rebuild their homes, the federation said.
In late November, the federation issued a revised appeal for Bangladesh, calling for 24.5 million Swiss francs ($22.2 million) to provide long-term support for more than 1.2 million people affected by Cyclone Sidr.
Bangladesh has asked the international community for $2.2 billion to rebuild the impoverished country's south and southwestern coastal areas, including the Sundarbans, the world's largest mangrove forest and a World Heritage site. (Reporting by Ruma Paul; Writing by Anis Ahmed; Editing by David Fogarty)