The Golden Globe winning actress was one of four bridesmaids for old pal, producer Melinda Relyea, whom she met while filming Sex and the City.
Relyea is also the vice president of SJP's Pretty Matches production company.
She attended the glamorous beach ceremony with husband of 17 years, Matthew Broderick, in Greenwich, Connecticut.
Despite her bridesmaid's star status, Melinda was centre stage in her Oscar de la Renta blue and white gown.
Earlier in the week, she gave fans a sneak peek of her strapless purple gown on Instagram and updated her followers with the day's festivities.
SJP is no stranger to wedding guest style as she posed with one very lucky bride for a special photograph at Lough Eske when she and her famous family were holidaying at their Donegal home in July.