Attorney generals in a multi-state working group on social networking had reportedly been negotiating with MySpace for protection to shield children from online dangers for nearly two years.
Roy Cooper, attorney general of North Carolina, said: "MySpace has adopted more than 60 specific changes in its design or function, in part because of the ongoing review and scrutiny that has been given it by law enforcement, parents and others."
Texas was the only state that declined to sign the agreement, which was signed off by 49 other states.
The Texas attorney general said he could not support the effort because MySpace did not agree to implement online identity technology to verify users' age. Instead, MySpace will take part in a new task force to examine potential safety tools.
However, the attorney's general could still force MySpace and other social networking sites to implement age-verification technology.
Cooper said: "We can still take those actions if we think it's necessary."
The agreement also requires MySpace to appoint an independent examiner for two years to monitor how the site handles consumer complaints.
Hemanshu Nigam, MySpace chief security officer, said MySpace had already incorporated most of the guidelines, including filtering images and video uploaded to the site, and it will implement others in coming months.
He said: "This is an industry-wide challenge and we must all work together to create a safer internet."
, which was acquired by News Corp in 2005, was listed as the third most popular social networking site in the UK behind and during November last year with a 19% market share, according to Hitwise.