FORTUNE — Dear Annie: Last night, for the zillionth time, I had to stay until 9:30 p.m. — missing my daughter’s piano recital — to finish a project because another member of my team went waltzing out the door at 5 p.m. without completing his share of the work. (The deadline was this morning, and “we” made it, no thanks to him.) Other people on our team have also picked up the slack for this person on many occasions, so it’s not just me, but I’m really starting to feel like a chump.
So far, he’s gotten away with slacking off because he’s very likable and fun to have around, and everybody has tiptoed around the fact that he’s not doing his job, but I really think it’s time to do something about this. Should I tell our boss what’s been going on? What do you think? — Steamed in Seattle
Dear Steamed: This person has saddled you with his work a zillion times, and you’re just getting mad now? You and your overburdened teammates are remarkably patient. But seething silently is probably just making things worse. “By not speaking up when someone isn’t pulling his or her weight, you’re tacitly giving that person permission to keep on with the behavior,” notes Kerry Patterson, co-founder of training and development firm VitalSmarts and co-author of a book called Crucial Confrontations.
Alas, your dilemma is far from unique. “When we’ve done surveys over the past 30 years, one of the top complaints that always comes up is ‘carrying dead wood,’” Patterson says. In an online poll of about 550 full-time employees earlier this month, for instance, 93% said they work with at least one person who isn’t doing his or her fair share.
Still, only one in 10 has confronted an under-performing coworker. “Most people worry that bad things will happen if they say something. They want to avoid conflict and unpleasantness, or even retaliation,” says Patterson. “It’s easier to just grit their teeth and do the extra work” — up to a point, anyway, and then look out.
“What usually happens,” he adds, “is that people wait until they are really fed up, and then they blow their stack. The trouble is, that doesn’t usually do any good and, what’s worse, it can backfire on you. Even if you’re completely in the right, losing your temper makes you look unprofessional and out of control.” And who needs that?
So what should you do that might actually help? First, don’t rat out the slacker to your boss, at least not yet. “You’ll never be a real team if you go running to the boss without talking to each other first,” Patterson says. Instead, make an appointment to speak with your errant teammate in private (maybe even over lunch, since he’s such a fun guy) and, before you meet with him, calm yourself down.
“It’s all in your attitude and the language you use. Don’t go in all angry and full of judgment, with the idea that you’re going to give him a piece of your mind,” says Patterson. “Instead, be curious. Find out how he sees the situation.” And stick with the facts. Say something like, “Last week, my understanding was that you’d be doing X and I would cover Y, but I ended up doing both. What was up with that? Did you understand this project the same way I did? How did you see your part in it?”
The point of this conversation is to reach an agreement on how the work will be divided from now on. “Don’t get too hung up on the past,” Patterson suggests. “Stay focused on what happens next: ‘I’ll be doing this, and you’ll do that. Right?’ The other person may not see it that way, but you need to find out how they do see it.”
Only if that discussion leads nowhere — if, for example, your teammate nods and smiles and goes right back to slacking off — do you involve the boss. “Even then, don’t go there on your own,” says Patterson. “Take your teammate with you and ask your boss to clarify how the work is supposed to be divvied up. Again, you’re not assigning blame, just seeking clarity.”
This meeting should put your coworker on notice that you’re no longer willing to be, as you put it, a chump. It also may lead to a useful discussion about what (besides sheer laziness or indifference) has been keeping this person from doing his job. “Sometimes it turns out that there’s an ability barrier, where the person lacks a necessary skill, so that some training is in order,” Patterson notes. “Or it could be that there’s some kind of personal issue, like an illness in the family, that is distracting him or causing him to always leave early.”
If the latter is the case, Patterson adds, “You might feel sorry for him, but you have to insist he find some way to work it out, most likely with some help from the boss. Fight the temptation to essentially say, ‘Oh, okay, I’ll keep doing your work for you.’ It’s not fair to you for his personal situation to make your life harder — and, if you’re not careful, you’ll have put yourself in a bind that you’ll never get out of.”
Talkback: Have you ever worked with someone who didn’t do his or her fair share? How did you handle it? Leave a comment below.