Most people picture a toxic colleague as someone who shouts. In reality, they are often perfectly charming in a meeting and quietly exhausting one-to-one: the person who needs a “quick favour” every afternoon, who copies your manager into a faintly critical email, or who asks what you are working on with a raised eyebrow. If you finish most days feeling wrung out and slightly annoyed at yourself, something needs to change. It doesn’t have to involve a dramatic confrontation in the kitchen.
Name the behaviour, not the person
“She’s difficult” will get you nowhere, with your manager or with yourself. Specific behaviours are easier to respond to, easier to evidence and much harder to dismiss. So write down what actually happens. Not “he undermines me”, but “on Tuesday he told the client my figures were provisional, in a meeting I hadn’t been told he was attending”.
Three or four entries are usually enough to show you the pattern. It might be last-minute requests, credit-taking, constant interruptions, or jokes that land as jabs. Knowing which one you are dealing with tells you what to do next. A colleague who is merely disorganised needs a paper trail. A colleague who is deliberately belittling you needs a different conversation entirely.
Decide what you are protecting
A boundary is a rule about your own behaviour, not an instruction for someone else. You cannot make a colleague stop messaging you at 10pm, but you can decide not to answer until the morning. Framed that way, boundaries become things you can actually control, which is why they work.
Spend ten minutes writing your non-negotiables for the next month. Keep them plain and realistic:
- I don’t take on work that hasn’t been agreed with my manager, however urgent it sounds.
- I don’t reply to messages after 7pm or before 8am.
- I keep my lunch break, even if I eat at my desk.
- I don’t hand over work without an email confirming what I did and when.
- I don’t discuss a colleague’s criticism of my work until I have had time to read it properly.
Notice how dull these are. That is the point. Boundaries that survive a bad Tuesday are boring, repeatable and easy to explain.
Scripts beat speeches
When you are caught off guard, the clever reply you thought of in the shower is no help. Have two or three short sentences ready instead. You are not trying to win an argument; you are closing a door politely.
The broken record
Repeat the same line, calm and unchanged, until the request goes away. “I can’t take that on this week. If it’s a priority, ask Priya to confirm it with my manager.” Then, if needed: “Same answer, I’m afraid.”
Buying time
Most pressure relies on you answering instantly. Refuse to. “Let me check my workload and come back to you by four.” “I’d rather read that properly than guess now.” “Can you put that in an email so I’ve got it?” That last one is quietly powerful: requests that look unreasonable in writing often evaporate.
Naming it once, lightly
If comments are pointed, a flat, unbothered response often works better than a lecture. “That sounded like a dig. Was it meant to be?” Then wait. Most people back down; those who don’t have just shown you what you’re dealing with, and you can decide what to do about it.
Change your habits before you change the person
You will get further by adjusting how work flows between you than by trying to fix someone’s personality. Try these in order:
- Move verbal requests into email or your team’s messaging tool, where there is a record.
- Send a short summary after any conversation where work was agreed: what, who, by when.
- Ask for agendas before meetings, and add your own items if you need to.
- Keep a dated note of incidents that affect your work, with what was said and who was present.
- Answer in writing when you would otherwise be ambushed in a corridor.
- Decline work that isn’t yours, in writing, copied to your manager where it’s reasonable to do so.
None of this is aggressive. It is simply the administration that protects you, and it makes any later conversation about the problem much easier to have.
When to bring in your manager
Escalating is not tattling, and you don’t need to have exhausted every option first. Go earlier if the behaviour is affecting deadlines, clients, your health, or your ability to do your job.
Bring three things: the pattern, the impact, and what you want. For example: “Over the last month, I’ve been asked to redo work after it was signed off, twice without being told. It’s added about a day a week and it’s affecting the project timeline. I’d like agreement on who signs off my work.” That is a business problem, not a personality clash, and managers find it much easier to act on.
If the behaviour amounts to bullying, harassment or discrimination, use your organisation’s formal policy rather than trying to manage it alone. A trade union representative, HR, or a trusted senior colleague can tell you what your options are. For anything with legal implications, take proper professional advice for your situation.
Look after your energy in the meantime
You cannot out-boundary a bad atmosphere overnight, so protect yourself while you work on it. Vent once to a trusted colleague, then stop rehearsing the argument on your commute. Take your breaks away from your desk. Keep a couple of work friendships outside your immediate team, so your sense of how things “normally” work isn’t shaped by one person.
If you are losing sleep, dreading Sundays, or feeling persistently low or anxious, that is worth taking seriously. Speak to your GP, and mention it to your manager if you can. Boundaries help, but they are not a substitute for support when your health is affected.
Your first week: a simple plan
Keep it small and doable. Write down your three non-negotiables. Pick one script and practise saying it out loud until it sounds like you. Move tomorrow’s verbal requests into email. Start a dated log with two entries. Then, at the end of the week, notice what changed.
You will not transform a difficult colleague, and that was never the job. The aim is quieter: to make your working day predictable, to keep your name attached to your own work, and to stop spending your evenings replaying conversations. Most of that comes from small, repeated decisions made in the moment, which is exactly why they work.
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