Gilbert: Laura Ingalls in Little House on the Prairie
The result has decided one of the bitterest rows in the Hollywood union's 69-year history in favour of the guild's moderates.
Gilbert, 37 - who played Laura Ingalls in 1970s TV series Little House on the Prairie - took 21,351 votes out of nearly 38,000 cast.
Rival Valerie Harper, 61, who starred in 1970s TV comedy Rhoda, received 12,613 votes.
Gilbert repeated her defeat of Harper in last November's election, the result of which was annulled after protests from the Harper camp of balloting irregularities.
Just under 28,000 ballots were cast in the first election, which saw Gilbert edging out Harper, the then favourite, by around 1,600 votes.
Turnout this time was high by SAG standards, with 41.4% of more than 91,000 ballots returned - the highest level on record for a presidential race
Two Harper allies won repeat victories to national office, M*A*S*H film star Elliot Gould as recording secretary and Kent McCord, of the 1960s police show Adam 12, as treasurer.
Accepting victory, Gilbert said the election had been rerun in a fair manner.
"The real winner is the democratic process," she added.