JERUSALEM — Prime Minister Netanyahu’s son must compensate a woman who sued him after he implied she was having an affair with his father’s chief political opponent, a court ruled Wednesday.

The court ordered Mr. Netanyahu’s eldest son, Yair Netanyahu, to pay more than $34,000 in compensation and $6,000 in legal costs to Dana Cassidy. Ms. Cassidy sued him for defamation in 2020 after he insinuated on social media that she was romantically involved with the man running against his father for prime minister at the time, Benny Gantz.

Over the course of the election, which ultimately returned Mr. Netanyahu to leadership, the younger Mr. Netanyahu posted a series of unsubstantiated statements implying that Mr. Gantz was having extramarital affairs, according to the ruling.

“The insinuation that the young activist had an intimate relationship with the head of the party, a married man who is decades older than her, could humiliate her and make her a target of hatred, contempt or ridicule,” Judge Ronen Peleg wrote in the ruling.

Yair Netanyahu first posted a screenshot of Ms. Cassidy’s Facebook profile on the platform “X,” formerly known as Twitter, writing, “Does anyone know who this is?”

He then reposted an article with a photo of Ms. Cassidy and Mr. Gantz hugging at a political event for Blue and White, Mr. Gantz’s centrist political party. At the time, Ms. Cassidy was an active member. The bottom of the picture says, “he made me a cup of tea and it turned me on,” according to the ruling.

In the post, the younger Mr. Netanyahu wrote, “to each his own cup of tea.”

Ms. Cassidy has told the Israeli press in the past that she dealt with a flood of online harassment in the wake of the posts. She did not immediately respond to a request for comment on Wednesday.

“The son of the prime minister ought to exert self-control,” Judge Peleg wrote in the ruling, calling the younger Mr. Netanyahu “evasive and stammering.”

Yair Netanyahu, who has served as a close informal adviser to his father, is known for posting incendiary messages on social media and has been involved in several defamation cases over the years. Earlier this year, a judge ordered him to pay $18,000 to a former lawmaker in Israel’s opposition Labor Party whom he called “ugly.”

The older Mr. Netanyahu heads Israel’s rightist government, which includes a number of lawmakers and ministers with close ties to his son.

Israeli media reported earlier this year that the prime minister and his wife, Sara, have urged the younger Mr. Netanyahu to stop posting on social media.

Mr. Netanyahu’s office did not comment on the ruling.