In the poll, 41 percent of people said they believed Sweden should join, 39 were opposed, and 20 percent said they did not know.
Since last year, support for NATO has increased by 10 percent, and opposition has declined by 11 percent.
"I'm surprised by the speed of the shift," Wilhelm Agrell, a professor in military intelligence, tells news agency TT. He wrote on Sunday in a debate article in Dagens Nyheter that Sweden should apply for NATO membership along with Finland.
The poll was carried out during the beginning of September, after the leaders for both the Center party and the Christian Democrats came out recently saying that they were positive to joining NATO. In doing so, they joined fellow opposition parties, Liberals and the conservative Moderates.