It is a source of tension in many workplaces—nonstop conversation from the office oversharer.

Oversharers spew gritty details about their romantic exploits, marital woes, financial problems, recent surgeries or the latest moves by their mothers-in-law—whether colleagues show interest or not.

Amelia Blanquera was beset for months by a co-worker who wanted to talk about his family problems, dating issues and experiments with new yoga styles. She tried to discourage him by moving to a desk at the center of their open office, making their conversations more awkward. She also donned headphones; if he popped up by her desk, "I made a big display of taking them out, and said, 'I'm trying to get some work done,' " says Ms. Blanquera, a New York City attorney and writer.

She drew the line when the co-worker brought out a tantric-yoga book to show her, saying firmly, "I don't have time." Over time, they negotiated an understanding that he wouldn't interrupt so much. "He needed a therapist or a best friend or a companion, which ultimately he got" when he began dating someone outside the office, she says.

More than 3 in 5 workers say they have at least one co-worker who overshares once a week or more, according to a survey of 514 professional and corporate workers by SurveyMonkey Audience. Oversharers often disrupt colleagues' work and risk damaging not only their own careers, but those of others. Intervening takes finesse, however, because oversharers are sometimes fragile and heedless of social cues. Many need direct, explicit feedback to break through the emotional needs or desires that keep them talking.

Kim Rosen

One attorney in Nancy Fagan's San Diego, Calif., divorce-mediation clinic didn't realize how her nonstop talk about her marital woes was affecting colleagues. The attorney was "using the office as her place to vent, process and try to find resolution," and co-workers were complaining, says Ms. Fagan, owner of the Divorce Help Clinic.

Ms. Fagan called the attorney into her office, reassuring her that her job wasn't in jeopardy, and instructed her to stop using the office to resolve her issues. Ms. Fagan also recommended that the attorney see a therapist, and the disruptive chatter stopped.

Some oversharing is linked to traits that are helpful on the job. Billy Bauer loves trumpeting the dollar value of his latest sales as director of marketing for Royce Leather, a Secaucus, N.J., maker of leather products. He recently announced to co-workers that he made $40,000 in sales in a week, and a few months ago boasted he had hit the $1 million mark for the second straight year.

Andrew Royce Bauer, Billy Bauer's brother, is chief executive of the company. He says he hasn't received any complaints from co-workers but does worry that his brother is "a bit overzealous" and has cautioned him that such openness could make other employees uncomfortable.

Billy Bauer says such announcements are part of the extroverted personality that makes him a successful salesman. "I don't temper or subdue that personality, regardless of the context," he says.

Bosses walk a fine line in trying to curb oversharing in an era when openness is in vogue. Matthew Reischer wants to create a family-like atmosphere at his legal-services startup, LegalAdvice.com. But he cringes when some employees share war stories about evenings spent drinking and socializing at a nearby bar. "It's tricky, because I don't mind hearing the stories when it's one-on-one," but the boundaries are different in the office, says Mr. Reischer, chief executive of Legal Marketing Pages Corp., New York City. He has privately asked two employees to set better boundaries.

Sharing personal information satisfies a human desire to connect with others and shape others' views of us, says Lisa Rosh, an assistant professor of management at Yeshiva University in New York. It activates the same reward pathways in the brain as those aroused by eating and sex, says a 2012 study in the Proceedings of the National Academy of Sciences. "People get a biochemical buzz when they talk about themselves," says Dr. Rosh.

Many managers strive to win co-workers' trust by showing authenticity and openness, says a Harvard Business Review article co-authored by Dr. Rosh and Lynn Offermann, a professor of organizational sciences and communication at George Washington University.

Personal stories work well when they're relevant to the task at hand and aimed at building teamwork rather than drawing attention to oneself. Dr. Rosh tells of a hospital executive trying to calm employees worried about their jobs in a planned reorganization. The executive told a story about having been laid off in the past and said she hoped to cut costs without layoffs. Persuaded that she understood their fears, employees calmed down, Dr. Rosh says.

Many oversharers disregard those guidelines. Some are self-absorbed and narcissistic and "think you want to know all the details of their lives," says Alan Hilfer, director of psychology at Maimonides Medical Center in New York City. Narcissists talk about important and trivial events as if they were equally significant, giving equal weight to " 'My mother died last week,' and 'I had chicken for dinner last night and it was the best chicken I ever had,' " he says.

Other oversharers feel vulnerable or anxious, causing them to "lose boundaries and reveal too much," Dr. Hilfer says. They may misunderstand therapists' advice to dispel anxiety by talking with others, he says.

Anxiety drives some people to say the first thing that pops into their heads, says Aimee Cohen, a Denver career consultant and author of "Woman Up," a book about overcoming unconscious obstacles to success. Women, in particular, tend "to lead with whatever they feel worst about," Ms. Cohen says.

Ms. Cohen advises clients to practice talking about themselves in positive terms. She also suggests avoiding certain topics, including the size of paychecks, sex, drugs, alcohol, medical problems, relationship dramas or negative views about the boss, co-workers, clients or company.

To curb a colleague's chatter, avoid judging or labeling. Instead, describe the impact oversharing has on you in a direct, honest way, Dr. Rosh says. For instance: "I prefer that you not talk about X, because it makes me uncomfortable or nervous and diverts my attention from work."

Write to Sue Shellenbarger at sue.shellenbarger@wsj.com