Housing charity Threshold says it took 71,319 calls in 2016.
As part of its annual report, it says it also helped 21,625 people during that time with tenancy issues.
The group says 29% of calls were in relation to situations where people were at risk of losing their homes.
Threshold also noted an increased complexity in queries, with many clients in need of "in-depth support and advocacy."
Of the calls received last year tenancy terminations and substandard accommodation ranked equally as the top two issues.
Some 13% of calls were queries by those seeking accommodation, pointing to reducing availability of rental properties - while issues related to rent reviews and invalid notices both accounted for 11%.
While 37% of those who contacted Threshold were in receipt of Department of Social Protection Payments, and 44% of clients were families with children.
Speaking at the launch of the report Threshold chair, Dr Aideen Hayden, said: "The unprecedented level of calls received by Threshold in 2016 is indicative of the financial and mental distress experienced by those living in the private rented sector, where there remains an acute shortage of supply.
"Individuals and families find themselves in dire situations as competition for homes at the bottom end of the rented market has led to greater poverty and the emergence of overcrowding and falling standards.
"We are particularly concerned with the rise of hidden homelessness where people who have already lost their rented homes are living with family members or friends and where the physical circumstances place pressure on relationships, which bring them one step away from homelessness."
Threshold chief executive, John-Mark McCafferty, added: "The Tenancy Protection Service has proven to be highly effective in preventing homelessness and keeping people in their home at a time where the cost of renting, and the scarcity of rental accommodation, is no longer a viable option for many.
"Since the Tenancy Protection Service launched in 2014, Threshold had prevented more than 10,000 people at immediate risk from losing their homes by the end of 2016.
"In Dublin, we identified 1,425 families as being at imminent risk of homelessness, with 601 families identified in Cork and a further 150 families in Galway.
"Families were identified as being at imminent risk of homelessness due to rent arrears, being given notice of termination, unaffordable rent increases or threatened illegal eviction."