Housing charity Threshold says nearly 300 tenants contacted it in November in fear of losing their homes.
It says this is the highest monthly figure to date this year.
November was also the busiest overall for the organisation - which took 7,639 calls last month.
This was a 29% increase on the October figure.
Threshold chief executive, John-Mark McCafferty said: "Threshold saves an average of five families a day from homelessness.
"Ireland is in the grip of a cruel and relentless national housing crisis and no other organisation tackles homelessness the way Threshold does - by keeping people in their homes.
"This is by far the most effective way to prevent homelessness.
"We are concerned about the November figures, which reflect the huge increase in families facing sudden rent increases and illegal evictions over the year.
"Last December we dealt with 151 clients who had received a tenancy termination, and if this trend continues, we expect that figure to be much higher for 2017."
Threshold chair, Dr Aideen Hayden added: "Ireland’s housing crisis is down to poor planning and it will not be solved through short-term measures alone.
"Threshold’s helpline responds to 76 calls a day from families in crisis - if we are to address homelessness effectively, greater emphasis and resources need to be placed in tackling the causes of homelessness.
"Most of these stem from the State’s overreliance on the Private Rented Sector and the problems within the sector regarding high and growing rent levels and increasing unaffordability; lack of security of tenure; and physical issues with rented properties such as standards, repairs, fire safety and energy efficiency."
Last year, Threshold’s emergency on-call service received 40 calls over the Christmas period.
The charity says it will provide this service again this year for individuals and households at risk of homelessness.
Information will be available on the Threshold website and by phoning the 1800-454-454 helpline.