Appearing on "Fox News Sunday," Feinstein was asked whether Senate approval is a certain.
"I believe it is," Feinstein said. "She is an amazing, warm and intelligent woman, and she actually brings to the court more experience in courts -- trial courts, appellate courts -- than any sitting member of the Supreme Court."
Feinstein said Sotomayor had "overcome adversity and disadvantage and carried on and done it basically by herself."
Appearing on the same program, Sen. John Cornyn, R-Texas, said he doesn't think Senate Republicans will filibuster the nomination.
"I think she'll be given a fair hearing," Cornyn said. "I personally, and all of my colleagues, have made the commitment to give her a fair hearing, treat her with the dignity we would expect every nominee to be treated."
The Senate Judiciary Committee is scheduled to open hearings Monday on President Barack Obama's nomination of Sotomayor to succeed Justice David Souter, who is retiring.
Cornyn said Republicans will focus on Sotomayor's "judicial philosophy."
"You know, the judge has given a lot of speeches, in addition to her official actions, where she's questioned whether judges can actually be neutral, whether there is such a thing as objectivity in the law, which means that judges are affected by their biases," he said.