Q. A mid-level professional at the company I run is constantly complaining about her job. Her performance is acceptable, but she comes to me with an unending stream of gripes about working conditions, and often involves her colleagues by copying them on complaining emails to me. What can I do to get her to stop poisoning the atmosphere? 

A. There are two problems here. One is your complaining employee, and the other could be you.

Every office has at least one squeaky wheel that makes noise about everything from the quality of the coffee in the break room to the company’s expense-reimbursement policies. Typically, this person is never happy with working conditions and will move on to a fresh grievance as soon as management addresses an old one.

Such a person can create a toxic atmosphere in the office. For one, they rope in colleagues who would never complain on their own. They can also create mass dissatisfaction that destabilise your workforce. A drumbeat of negativity gets in the way of everyone’s performance.

The first step is to consider your role as the manager in this situation. Let’s assume that you are a decent and ethical boss who wants your people to work in a friendly environment, at least comfortable enough so they will be content to stay.

First, consider whether your complaining employee is the canary in the coal mine, says Stevenson Carlebach, president of Eque LLC, a communication-effectiveness consulting firm in Connecticut in the US. Since employees tend to take a positive tack with the boss, managers usually think everything is going well — it also means they believe their staff likes them more than they actually do. It’s possible that the complainer is in fact the only one who is telling it like it is. 

“Talk to employees you trust to tell you the truth,” Carlebach says. “Ask them what is accurate about the complainer’s comments.” Then go back to the complainer and ask her to help you address those specific problems. Simultaneously ask her to acknowledge when you’ve fixed something she flagged, as well as existing good points about working in the office.

Another point to consider is whether you are successfully making your employee feel that you are listening to her. “When people don’t feel heard, they tend to repeat themselves, often increasingly loudly and stridently,” Carlebach says. “If I were the boss here, I would assume that part of cause of the endless complaints is my not having demonstrated sufficiently that I heard the speaker.”

It’s normal to address complaints by trying to get the other person to see the situation your way. Since you don’t see the same problems she sees — you think the coffee is just fine, you don’t agree that the expense policy needs to be changed — she might feel that you are just trying to get her to shut up. Sit down with the complainer and make sure that she hears that you take her concerns seriously, Carlebach says.

Be careful to avoid making your employee feel as though you blame her. (Of course you blame her. Just don’t show it.) The key is to make her understand how her constant complaints are impacting you and the rest of the office, while simultaneously reassuring her that you believe she has good intentions.

Carlebach suggests phrasing it this way: “When you send emails complaining about working conditions and copy your colleagues, I feel undermined.  I worry that a negative perspective can become infectious and I don’t want everyone to be focused only on what’s not working.  At the same time, I’m sure that you have good intentions — my guess is that you have real concerns and are trying to address them.”

Then request, politely, that she bring her concerns to you first without copying others on emails, and that she try to recognise what’s good about life in your office. Surely not every aspect of her workplace is unpleasant.

What if your inquiries confirm that she is the only one on your team who sees these problems? In that case, her efforts to spread unhappiness around your workplace could be more detrimental to the team than having her is worth. If you think her pot-stirring undermines office morale and productivity more than her mediocre job performance raises it, you may want to consider easing her off of your team. The rest of your team will thank you.

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Work Ethic is a twice-monthly column on BBC Capital in which we consider the ethical and interpersonal dilemmas that workers face around the world. We welcome knotty questions from readers at workethic@bbc.com.