Karine Jean-Pierre began her debut briefing as President Biden’s press secretary on Monday by acknowledging the unusual nature of her presence behind the White House lectern. “I am a Black, gay, immigrant woman, the first of all three of those to hold this position,” she said.

Left unsaid were the other ways in which her path to becoming the president’s chief spokeswoman sharply diverged from that of her predecessors.

Ms. Jean-Pierre was born in the Caribbean to Haitian parents, who lived paycheck to paycheck after immigrating to New York City. Her conservative Catholic family, she has written, carried “so many secrets, so much unexpressed pain.” As a child, Ms. Jean-Pierre was sexually abused by a cousin. Her mother went decades without acknowledging that her daughter was a lesbian. And in her early 20s, despondent at a career setback, Ms. Jean-Pierre attempted suicide.

She grounded herself in political advocacy work, rising from meeting with constituents in Far Rockaway, Queens, to a job in the Obama White House. But while Ms. Jean-Pierre spent years as an MSNBC pundit and national spokeswoman for the liberal group MoveOn.org, she rarely had to tackle a daily grilling from an adversarial press corps.

Ms. Jean-Pierre, 47, starts the job at a particularly difficult moment for the Biden administration, which has struggled to persuade the public to support its agenda. She will need to address record-high inflation, a resurgent coronavirus and looming midterm elections that many Democrats expect to be a shellacking.

Her predecessor, Jen Psaki, became a star among liberals for her rarely ruffled demeanor and lively tussles with Fox News journalists. (She is headed to a new gig at MSNBC.) Ms. Jean-Pierre has so far shown a more informal style: less crisp than Ms. Psaki, but also disarming, laughing at herself when she stumbles over a word or two.

“There’s something a little introverted about her, which is an odd thing to say about someone who is now the principal spokesperson for the president,” said Patrick Gaspard, a former United States ambassador to South Africa and political director for former President Barack Obama, as well as a mentor to Ms. Jean-Pierre.

Mr. Gaspard, who is also Haitian American, said he recognized in her a fellow immigrant navigating an unfamiliar and privileged space. “They have some sense of their capacity and their talent, but are hesitant as they weigh in because they’re not sure if they’re using the right idiom,” he said. “Some blast through and rise to the occasion and become powerful in their own place, and Karine is absolutely an example of that.”

Ms. Jean-Pierre worked briefly as Kamala Harris’s chief of staff during the 2020 campaign, once fending off an interloper who accosted Ms. Harris onstage. She became Mr. Biden’s principal deputy press secretary when he took office.

Still, she lacks Ms. Psaki’s yearslong relationships with Washington journalists — the sorts of connections that can yield benefits behind the scenes — and the seasoning of press aides who regularly go back and forth with a pack of combative reporters. She was mocked by Fox News this week after tentatively answering a question from the network’s White House correspondent, Peter Doocy, about Mr. Biden’s plans to fight inflation.

Ms. Psaki, who has called Ms. Jean-Pierre her “partner in truth,” said in an interview that her successor understood that a press secretary needed to address a broader national audience, not just reporters gathered in the West Wing.

“The room is so small, it’s easy as a human being to forget that,” Ms. Psaki said. “Karine knows how to capture a moment, to make a moment, and speak in a way where people sitting at home will understand and relate.”

Ms. Jean-Pierre was born on Martinique, then lived briefly in France before her parents immigrated to Queens. (She has two younger siblings, a sister and a brother; one brother, Donald, died before she was born.) Her mother, a retired home health care worker, never learned to read English; her father, a New York City cabdriver, still works part-time, though the taxi medallion he invested in years ago has plummeted in value.

She grew up in a strict Catholic household, where trauma was not discussed. In her 2019 memoir, “Moving Forward,” she wrote that she was sexually abused as a child, between ages 7 and 10, by an older male cousin; sometimes, she hid from him in an attic crawl space. The abuse ended, she wrote, after a female relative sensed a problem and intervened.

As a teenager, Ms. Jean-Pierre harbored another secret: She was attracted to other women. The prospect of disappointing her conservative parents was so upsetting that she briefly considered becoming a nun. At 16, arguing with her mother, she abruptly confessed that she was a lesbian. “I could see the revulsion on her face,” Ms. Jean-Pierre wrote. “For this she had sacrificed everything?” She and her mother did not speak about her sexuality for years afterward.

Her parents pushed her to become a doctor, and she studied life sciences as a commuter student at the New York Institute of Technology on Long Island. But Ms. Jean-Pierre performed poorly on her Medical College Admission Test. She became convinced she had failed her parents in a profound way. “My entire world crumbled,” she wrote in her memoir.

One afternoon, Ms. Jean-Pierre recounted in her memoir, she parked her car inside her family’s garage, sealed the doors and turned on the engine. “Everyone will be happier when I’m gone,” she recalled thinking to herself.

Ms. Jean-Pierre does not know how long she was unconscious. She was shaken awake by her sister, Edwine, who had discovered the running car in the garage. Her pants were wet with urine; she later disposed of the soiled clothes in an outdoor bin to avoid detection. To this day, other than her sister, her family has never spoken with her about her suicide attempt.

“I put it in the book because I want to help people,” she later told Judy Woodruff of PBS. “I want anybody who has ever felt that way to feel like there is a way out and to know there is a way out.”

(Ms. Jean-Pierre now lives in the Washington suburbs with her longtime partner, the CNN correspondent Suzanne Malveaux, and their 7-year-old daughter. Ms. Jean-Pierre’s mother, she has told friends, is doting and accepting of her personal life. CNN said Ms. Malveaux will not cover politics while Ms. Jean-Pierre is press secretary.)

After college, Ms. Jean-Pierre did odd jobs, including a stint at Estée Lauder and a conservation group where she protected piping plover nests. Encouraged by a mentor, she enrolled at Columbia University’s School of International and Public Affairs. She received a partial scholarship, but still has thousands of dollars of student loan debt.

Teachers including David N. Dinkins, the former New York City mayor, sparked an interest in politics. After starting out as an aide to two members of the New York City Council, Ms. Jean -Pierre joined the presidential bid of John Edwards in 2008. She briefly worked for former Representative Anthony D. Weiner, and later helped lead campaigns for Letitia James, now the New York state attorney general; and Martin O’Malley, a Democratic presidential candidate in 2016.

She became a political aide in the Obama White House in 2009, forging a friendship with then-Vice President Biden during campaign stops in the Northeast. Mr. Biden appears only once in Ms. Jean-Pierre’s memoir, but she writes warmly about their first conversation on Air Force Two in 2009, recalling Mr. Biden as “the sweet, kind ‘Uncle Joe’ you read about.”

In her memoir, Ms. Jean-Pierre wrote that it was “inconceivable, really, that anyone from our family could get to the White House.” On Monday, she was prompted by a reporter to talk about the significance of her new role. “What I hope is that young people get to dream big, and dream bigger than they have before, by seeing me stand here,” Ms. Jean-Pierre replied.

Then she returned to the work of promoting her boss.

Asked if she viewed the press secretary’s role as advancing Mr. Biden’s interests or delivering “the unvarnished truth,” Ms. Jean-Pierre did not miss a beat. “I actually think that’s hand-in-hand,” she said. “I don’t think that there is any separation to that.”

Alain Delaquérière contributed research.