The site was responding to a call from state attorneys general in the US to provide a list of offenders on its roster.
MySpace and rival site Facebook have committed to making their sites safer for the growing number of young users.
However, Facebook's measures to keep sex offenders off its site have been called into question.
The 90,000 sex offenders found on MySpace represent a significant increase and the figure is nearly twice that predicted by MySpace officials last year in a preliminary estimate.
Connecticut attorney general Richard Blumenthal, who is spearheading efforts in the US to make social networking sites safer for children, was not surprised by the number, telling the AP news agency that it "provides compelling proof that social networking sites remain rife with sexual predators."
Further moves by both sites to tighten safety include stricter age verification and limiting contact between under- and over-18s.
It is not the first time that MySpace has removed sex offenders from its site; in 2007 some 29,000 users were blocked for the same reason.
For that effort, MySpace worked with security company Sentinel to develop a database called that matched user profiles to data on convicted sex offenders.
Facebook does not use the Sentinel database, but employs its own "innovative and complex systems to proactively monitor the site and its users", according to a statement.
An investigation by website TechCrunch cross-referenced a list provided by Sentinel against Facebook users and found more than 8,000 potential matches.
In its own investigation following TechCrunch's find, Facebook disabled more than 4,000 accounts with user IDs associated with those on the list.
Facebook spokesman Barry Schmidt added that the external investigation was flawed, and that Facebook's own tools were more effective.
"Facebook does not allow the same investigations by an outsider as by insiders," he said.
Facebook has also been asked to provide a roster of sex offenders among its ranks for the state attorneys general, but has not yet responded.
Speaking to the BBC, a Facebook spokesperson was unable to go into detail about its timeline.