Three-quarters of charities expect demand for services to continue to increase significantly over the next year, at a time when 81% of groups expect their own financial position to deteriorate, the Scottish Council for Voluntary Organisations (SCVO) said in its annual State of the Sector report.
It said that 63% of charities and third sector organisations will be affected by the reforms, which are being brought in over the next four years in order to save £10 billion across the UK.
SCVO chief executive Martin Sime described the welfare cuts as criminal, with far-reaching effects on Scotland's most vulnerable citizens.
He said: "It's clear from this research that Westminster's criminal cuts to welfare are putting so much pressure on charities' services that some will struggle to keep up with demand from people and families in Scotland.
"The unprecedented worry and uncertainty surrounding the cuts is hitting the poorest the hardest as they face an endless cycle of appeals, bureaucracy and misinformation.
"All this, on top of trying to get by on a day-to-day basis, is pushing people and families to breaking point."
The sector in Scotland has already estimated it will lose around £200 million in public funding from Holyrood by 2014 as a result of the UK Coalition cuts.
Around 200 charity leaders from across the country will gather in Edinburgh today to discuss the cuts.
A key part of the Welfare Reform Act is to replace Disability Living Allowance (DLA) for eligible working-age people with a Personal Independence Payment (PiP). Under the changes, two million claimants will be reassessed in the next four years, with only those considered to be in need of support qualifying for the new payment.
The long-term unemployed could also see their benefits cut under Chancellor George Osborne's reforms.
Around 57% of charities which are engaged in welfare activity are providing crisis support, with 69% currently giving advice on benefits north of the Border.
Further pressures on services will be endured by charities given that 80% of welfare reforms have still to take place, SCVO said.
Graeme Brown, director of Shelter Scotland, said his organisation was preparing for a "perfect storm" of cuts, high unemployment and living costs that would bring a rise in homelessness.
Tom Greatrex, MP for Rutherglen and Hamilton West (Labour), said both the CAB offices in his constituency "will tell you that their workload has massively increased at a time of huge challenges to their own set-up".