The poll, conducted Oct. 21-22 by the MassINC Polling Group, has a 4.4 percent margin of error.
The last time pollster Steve Koczela surveyed voters for WBUR earlier this month, he found Brown ahead by four points.
"The last poll that we did happened to coincide with would have to be described as the worst week of the entire campaign for Democrats," Koczela said. "It was right after the first presidential debate, where President Obama gave what would have to be described as a pretty lackluster performance.
"When you go from a four-point lead for one candidate to a five-point lead for another candidate, it is a meaningful change, definitely," Koczela said.
That previous poll was also conducted before the latest debate between Brown and Warren. In that debate, Warren pointed out that Brown has voted against equal pay for women.
"He's gone to Washington and he's had some good votes, but he's had exactly one chance to vote for equal pay for equal work, and he voted no," Warren said at that Springfield debate.
Brown actually voted twice against a Democratic proposal that would have put the burden on employers to show why women should be paid less than men. Brown, along with other Republican moderates, such as Maine's Olympia Snowe and Susan Collins, voted against the measure because he believed it would cost jobs.
Warren's line of attack seems to be working. In our latest poll, she now has a 13 percentage point lead among women.
Earlier WBUR Senate Poll Results:
This program aired on October 24, 2012.