"Brothers and Sisters" star Rob Lowe has been in a legal battle with former nanny Laura Boyce since last year -- and scored a victory over the babysitter in court!

Lowe sued Boyce last year after she blabbed about his family's private life -- alleging that Rob's wife Sheryl liked to walk around naked. Yesterday, a judge sided with Rob, rejecting Laura's argument that the confidentiality agreement was invalid.