Research carried out by Survation for the Scottish Greens shows 56.9% of people are either strongly in favour or somewhat in favour of the move.
Less than a quarter (22.2%) of those surveyed said they are against the proposal - which Green MSP Mark Ruskell is trying to pass at Holyrood.
Transport Secretary Michael Matheson has already told MSPs there are a number of “challenges” posed by Mr Ruskell’s Member’s Bill.
But the Green MSP called on the Government to back his Restricted Roads (20mph Speed Limit) (Scotland) Bill after the poll found a majority in favour of the lower limit.
When “don’t knows” and those with no opinion are excluded from the poll, 72% are in favour of a 20mph speed limit.
Mr Ruskell said: “All the evidence demonstrates that introducing a 20mph limit in residential areas across Scotland would save lives.
“We’ve known that a majority of the public have backed safer streets for some time, and it’s great to see an ever clearer majority in this latest poll.
“It’s clear that people across the country recognise the benefits of introducing a default 20mph limit in their communities.
“Given the evidence, and the public backing my proposition has, it is now time for the Scottish Government to get behind my bill, ensuring that we put the lives of children ahead of maintaining the status quo.”
MSPs scrutinising Mr Ruskell’s proposals have been told by Police Scotland that enforcing a reduced speed limit would “not be a priority” for officers “because the majority of casualties are on faster speed roads”.
Mr Matheson has also said there is no money in his budget to meet the costs associated with cutting the speed limit, such as replacing existing signs.