The study, which was also sponsored by the Pew Forum on Religion & Public Life, interviewed 2,000 American adults by telephone between July 7, the date of the first terrorist attacks on London, and July 17. The margin of error for the study was plus-or-minus 3.5 percentage points.
A majority, 55 percent, of those surveyed expressed a "favorable" view of Muslim Americans, a figure that has risen from 45 percent before the 9-11 attacks.
Fewer people, 39 percent of those surveyed, said they hold a "favorable" view of Islam in general.
The survey reported that the number of Americans who believe Islam encourages violence is falling, with 36 percent of respondents ascribing to that view, down from 44 percent in 2003.
Basic knowledge about Islam was found to correlate with favorable views of the world's second-largest religion.
About half of those surveyed were able to identify the Quran as the Islamic holy book, and the same number correctly identified Allah as the Muslim name for God.
Among those with a basic knowledge of Islam, 61 percent of those surveyed expressed a positive view of Muslims, and 49 percent had a favorable opinion of Islam. Among those with the lowest knowledge of Islam, the favorability ratings are 47 percent and 24 percent, respectively.