The latest poll shows that Scots who are against independence are in the lead by four points.
An ICM poll published in the Scotsman newspaper, which was conducted between 12 and 16 September, shows that 52% want to stay within the 307-year-old union.
This is the latest poll to show that while the gap is closing between the two campaigns, the No vote is still in the lead.
However, the pro-independence campaign believes that the voting gap is small enough to secure a win.
"This is hugely encouraging for Yes - the six-point narrowing of the gap since the last comparable poll shows that Yes has the momentum as we approach referendum day," said Blair Jenkins, CEO of Yes Scotland.
"People know that a Yes vote is Scotland's one opportunity to achieve job-creating powers, protect our NHS from the damaging impact of Westminster cuts and privatisation, and ensure that never again do we get Tory governments imposed on Scotland that we have roundly rejected.
"This poll - like all the recent polls - shows that we are in touching distance of success on Thursday. The referendum is on a knife edge, and this will spur on everybody who wants and is working hard for a Yes to redouble their efforts."
Scottish people will vote in an independence referendum on 18 September 2014, and will be asked the straight "yes/no" question: "Should Scotland be an independent country?"
Prior to the ICM poll, two others showed that the No vote has regained the lead by a few points, after a shock survey by The Sun placed the Yes vote in the lead for the first time.