Editor's note: Inc.com columnist Alison Green answers questions about workplace and management issues--everything from how to deal with a micromanaging boss to how to talk to someone on your team about body odor.

A reader writes:

I've had an employee come tell me about some problematic behavior he witnessed from another employee. It's serious enough that not addressing it isn't an option, but the employee who told me about it asked me not to reveal that the information came from him. However, no one else saw it happen. What's the best approach to address this without violating his confidentiality?

You have a couple of options when an employee tells you something in confidence in a situation like this.

In general, I believe that your bias should be toward respecting requests for confidentiality. Otherwise, your employees will be less likely to come to you with information that you want to hear about, and that's not good. You want your employees to feel confident that they can speak to you without being outed.  In most cases, there's a way to act on information without attaching the person's name to it.

But not every time.

In this case, I'd first try explaining to the employee who came to you that what he observed is serious and something you need to address. Ask him to reconsider and to allow you to share what he told you. Sometimes, simply pointing this out to people will get them to agree to it. (And people appreciate being asked, rather than having you plunge ahead without their permission.)

If the employee doesn't agree, however, your options are:

1. Try to witness the behavior yourself. In cases where the behavior is likely to be repeated, you can look for opportunities to observe it firsthand--by coming by when you're not expected, digging a little more deeply into work than you normally would, and so forth. If you can spot it yourself, you can address it without violating the other employee's confidence. I've had employees tip me off to a problem before, and once I knew what was going on, I could easily look around and find evidence of it myself. In some situations, this could be your best option.

2. Tell the employee that you're sorry but the issue is so important that you need to be able to use the information. Say that you'll keep his name out of it, but since he's the only one who observed it, you can't guarantee that the other employee won't draw conclusions about how you were tipped off. You can also tell him--and this is important--that if the other employee gives him any trouble about it, you'll intervene and make it known that that's unacceptable.

(Keep in mind too, there are some things you're obligated to address, no matter how strongly the reporting employee asks you not to. For example, managers have a legal obligation to address sexual harassment if they learn about it; companies have an obligation to investigate harassment reports, even if the reporter asks them not to.)

And in general, when employees come to you and ask to talk in confidence, it's wise to say something like, "I'd really love to talk, and I appreciate you coming to me. I shouldn't promise that I'll be able to keep it confidential, because that might make it impossible for me to act on, but I can promise that if it is something I need to act on, there won't be any fall-out for you for having shared it with me." That will often get to the heart of what employees requesting confidentiality really want--assurance that they won't suffer consequences for talking with you.

Want to submit a question of your own? Send it to alison@askamanager.org.