In the middle of the night, Uyen Nguyen trudged through a grassy marshland with her mother and three siblings until they reached the edge of the ocean, where a small, dilapidated fishing boat was beached on the sand. It set off with 31 people packed on it.

It was 1985, a decade after Saigon had fallen, and their final attempt at fleeing Vietnam. Days later, the boat’s engine sputtered out, stranding the passengers at sea for about a month and forcing them to catch rainwater to sustain themselves. Ten people died, including Ms. Nguyen’s mother and two of her siblings. The others, including Ms. Nguyen, 10, and her 15-year-old brother, were rescued by fishermen and taken to a refugee camp in the Philippines.

Ms. Nguyen thought of that escape after seeing images of Afghans crammed on U.S. military planes in August, desperate to leave a country ravaged by a decades-long war. The unmistakable parallels, she said, have compelled her to help Afghans whose situation is similar to what she experienced.

“We can’t just sit back, especially since we’re either refugees or children of refugees,” said Ms. Nguyen, 46, an entrepreneur in Seattle who eventually immigrated to the United States with her brother as unaccompanied minors. “I don’t see an option not to do something.”

The Vietnam War has long stood as a symbol of American failure, with thousands of Vietnamese left behind after American troops swiftly withdrew and Communist forces toppled Saigon. For many who made it to the United States, watching the chaotic exit of American allies unfold in Afghanistan as the Taliban captured province after province evoked reminders of their own harrowing experiences fleeing their home country. But the painfully familiar scenes have also served as a catalyst for Vietnamese Americans across the country to mobilize in support of the Afghans. Many have offered their homes, organized fund-raisers and begun political advocacy campaigns.

About 64,000 evacuees have arrived in the United States since the Taliban seized Kabul over the summer, with the majority spending weeks on military bases before they are resettled. Those Afghans are now rebuilding their lives in an unfamiliar country, just as thousands of Vietnamese did over 40 years ago.

One day after the Afghan government collapsed, Ms. Nguyen texted a group of friends and proposed starting an organization that would recruit Vietnamese American families to host the Afghans streaming into the Seattle area. The five friends founded Viets4Afghans, which initially aimed to enlist 75 families — a nod to the year Saigon fell. More than 100 have volunteered.

Thanh Tan, 40, a journalist and filmmaker in Seattle who helped start the group, said her father, a South Vietnamese officer, decided to leave Vietnam after being sent to a re-education camp for six months following the war’s end. Like other allies of American forces, he was targeted for reprisal. He escaped by boat in October 1978, making it to Malaysia before arriving in Olympia, Wash.

Ms. Tan’s parents would often tell her stories about the Americans who helped them find jobs and resettle. Some befriended her parents, inviting them to their homes and offering meals. Vietnamese people who had resettled in America earlier also helped her father find work cleaning restaurants and schools while he took community college classes.

Her group now hopes to do the same for Afghans arriving with few belongings or relatives in the country. Although Ms. Tan acknowledged that there are clear differences between the two wars, she said there was a shared experience among the refugees.

“We understand the experience of what Afghans are going through in a way that very few others can,” she said.

Among those taking in refugees are Thuy Do, 39, a family physician, and her husband, Jesse Robbins, 39, a self-defense instructor, who have hosted two families in Seattle in a second home they own.

The father of one of them, Abdul Matin Qadiri, 46, said he, his wife and four children moved into that home in recent weeks. Ms. Do and Mr. Robbins have stopped by to spend time with them, Mr. Qadiri said, bringing items like a teapot and a television.

“We are happy, very excited,” Mr. Qadiri said through a translator.

Ms. Do, who fled Vietnam with her family in 1991, said they found shelter with a distant relative and a family friend for a few weeks once they arrived in the United States.

“It’s nice to pay it forward a little bit,” Ms. Do said.

It is unclear just how many Vietnamese Americans are welcoming Afghan evacuees, but Krish O’Mara Vignarajah, the president of the Lutheran Immigration and Refugee Service in Baltimore, estimated that hundreds of Vietnamese Americans have reached out to the agency and volunteered to host or sponsor Afghan refugees.

“I see it over and over again,” she said. “People who are on the receiving end of this work want to provide it to others.”

For Abdul Aman Sediqi, 36, who arrived in Houston with his wife and two sons after fleeing Kabul on Aug. 16, Tram Ho was instrumental in furnishing their apartment.

They first met at a Walmart, where Ms. Ho and her family helped pick out plates and kitchen utensils, along with Superman-themed clothing for Mr. Sediqi’s sons, who are 1 and 3 years old. The two families communicated through Sanya Wafeq, Mr. Sediqi’s case manager at the Y.M.C.A. International.

At first, Mr. Sediqi said, he did not know why Ms. Ho wanted to purchase items for his family. But after she told him that she was a refugee from Vietnam, he said he understood.

“That family had the same experience like us, leaving everything behind,” he said in an interview that was translated by his case manager.

Ms. Ho, 52, a doctor who fled Vietnam when she was 12, said she assured Mr. Sediqi that his family would eventually adjust to life in America, like her family did when they arrived in Houston decades ago.

“This is a land of opportunity,” she told him. “Just work hard. Your American dream will be fulfilled.” She said her father worked as a mechanic to support his six children through college.

Ms. Ho recalled the difficulties of picking up English when she first moved, but told Mr. Sediqi that his children would probably be able to learn the language quickly because they were much younger than she was.

In Springboro, Ohio, Daklak Do has pledged to hire at least 15 Afghan refugees at his company, Advanced Engineering Solutions, which supplies tools and equipment for the automotive and aerospace industries.

Mr. Do, 65, fled Vietnam in 1980 by boat with his brother and nephew. After spending two years in a refugee camp in Indonesia, he arrived in Ohio and got a job as a dishwasher at a Bob Evans restaurant. He said he wanted to “return the favor” to Americans who accepted him decades ago.

“They gave me an opportunity to go school, to open my own business,” he said. “I really appreciate that, and that’s why I want to return that to the people who are just like I was.”

Other Vietnamese Americans are organizing fund-raisers to collect donations for resettlement agencies. The Progressive Vietnamese American Organization, which has called on the Biden administration to ensure that high-risk Afghan refugees are not subject to a numerical cap, has raised about half of its $40,000 goal, said Minh-Thu Pham, a board member of the group. The organization will also provide career mentorship to Afghans through a partnership with Upwardly Global, a nonprofit that helps immigrants and refugees enter the work force.

Nam Loc Nguyen, 77, the former director of the immigration and refugee department of Catholic Charities at the Archdiocese of Los Angeles, helped organize a live telethon fund-raiser that aired on a Vietnamese-language channel last month. The concert, which featured performances from Afghan and Vietnamese singers, raised more than $160,000, he said. The money will be split between the Afghan Literacy Foundation and the Lutheran Immigration and Refugee Service.

Mr. Nguyen, a well-known M.C. in Huntington Beach, Calif., said the American withdrawal in Afghanistan reminded him of the anguish he felt in 1975 after leaving behind his family in Vietnam, days before Saigon fell.

His sister, who had worked for the U.S. government, was supposed to be evacuated along with their parents and nine other siblings. Mr. Nguyen, a war correspondent for the South Vietnamese military, was meant to stay.

On April 25, Mr. Nguyen’s friend, a high-ranking government official, persuaded Mr. Nguyen to accompany him to Tan Son Nhat airport. Mr. Nguyen initially protested. He had no documents, he said, and he probably would not be allowed through. His friend insisted he come anyway. Mr. Nguyen did get into the airport, and his friend told him to stay so he could reunite with his family.

Mr. Nguyen waited for his family to arrive, scanning bus after bus carrying evacuees. Days later, a U.S. Marine warned that the Communists would soon attack and that he should take the next flight out. Although his family had yet to appear, Mr. Nguyen boarded a plane at midnight on April 28. He stayed at a refugee camp in Guam before moving to California.

Only his father escaped that year, resettling in Belgium before eventually joining Mr. Nguyen in the United States. Over the next 14 years, his remaining 11 family members fled one by one.

Mr. Nguyen said he cried as he watched the last plane depart from Kabul, recalling how he left on one of the last flights out of Vietnam.

“That is why Vietnamese people want to help out,” he said. “Because it is the same pain that we went through.”