It was the first time women stood as candidates in a poll in the conservative Muslim kingdom, and most of the voters were men.
Election monitors had predicted one woman at best would be voted into office, according to reports.
“I’m happy, but I’m still under shock,” said Lama al-Suleiman, one of the two winners, speaking to AFP.
“It’s a big leap for Saudi women, an answer to what people want,” she said.
Ms Selieman, a 39-year-old mother of four, and her fellow female winner Nashwa Taher ran on a list of heavyweight business people and industrialists.
She holds a PhD in nutrition from Kings College in London.
Both women have vowed to back a centre which helps women in business and those working from home.
There were 12 board seats up for grabs, and only 100 women among almost 4,000 chamber members who cast ballots.
“We should give them (women) a chance because they have little representation in society,” one male voter said Tuesday, adding he had voted for four women.
Seventeen women were among the 71 candidates in the elections which took place from Saturday through Tuesday.
The win comes several months after landmark municipal elections across oil-rich Saudi Arabia from which women were barred but which were credited by many for heightening public interest in the chamber polls in the Red Sea city and turning them into a hotly-contested race.
Businesswomen cast their ballots on the first two days and businessmen on the following days, in line with traditions whereby Saudi women do not mix in public with men other than relatives.
The fact that women, who previously were entitled only to vote for the Jeddah chamber’s board of directors, stood as candidates “was also an unusual event which contributed to making this election unusual,” said Othman Basaqr, a member of a task force which assisted the elections committee.
Trade and Industry Minister Hashem Yamani is due to appoint an additional six members to the Jeddah chamber board.
The polls were rescheduled from late September by Yamani specifically to enable women to stand after the elections committee linked to his ministry had rejected the candidacies of seven women.