Friday's Dahaf poll, published in the Yediot Ahronot newspaper, is consistent with a recent trend showing that support for the withdrawal from the Gaza Strip and four West Bank settlements is plunging, while opposition is increasing.
The poll was taken on Thursday after the Supreme Court overwhelmingly ruled the pullout is legal.
Only 53% of those questioned for the newspaper's survey said they supported Israeli Prime Minister Ariel Sharon's disengagement plan while 38% said they were opposed.
When the last poll was held in February, 69% had said they supported the withdrawal while 27% were opposed to it.
It is the second poll this month to show that support for the pullout, due to begin in mid-August, is ebbing away. The Maariv daily found last week that only 50% now support disengagement while 34% are against it.
The latest Yediot survey was conducted by the Tel Aviv-based Dahaf institute and questioned 501 people. The margin of error was 4.4%.
Despite the fall in support, Sharon reiterated, in a speech late on Thursday, that he was determined to implement his plan, which he said would bring greater security to Israelis.
"I assure you that the disengagement plan will be implemented. It is the right and best possible step for the state of Israel," he told a gathering of scientists.
"I also believe that following this step, which is a very difficult and painful step, security in Israel will increase, and I also believe that investments will grow."