A single toxic team member can destroy an otherwise healthy team's morale, productivity, and culture. Whether the toxicity manifests as bullying, passive aggression, chronic negativity, or undermining behaviour, addressing it is one of your most important responsibilities as a manager. This guide helps you identify, confront, and resolve toxic behaviour before it spreads.
Identifying Toxic Behaviour Versus Difficult Personalities
Not every difficult interaction signals toxicity. Some engineers are blunt communicators, introverted, or opinionated without being toxic. The distinction lies in the impact: toxic behaviour consistently damages other people's ability to do their work, creates a hostile environment, or undermines team trust.
Common toxic patterns in engineering teams include publicly humiliating colleagues during code reviews or meetings, taking credit for others' work, spreading negativity that demoralises the team, refusing to collaborate or share knowledge, and engaging in passive-aggressive behaviour such as agreeing in meetings but undermining decisions afterwards.
Pay attention to signals from the rest of the team. If multiple people avoid working with a particular individual, if talented engineers are leaving or requesting transfers, or if team engagement drops noticeably, a toxic team member may be the cause even if the behaviour is not overtly visible to you.
Documenting the Behaviour and Preparing for the Conversation
Before confronting the individual, gather specific evidence. Document dates, contexts, and the exact behaviour observed - not your interpretation of it. 'In the 15 March code review, you wrote: Your approach is idiotic - just use the pattern I suggested' is documentation. 'They are rude in code reviews' is not.
Consult with your HR partner before having the conversation. They can advise on company policies, legal considerations, and documentation requirements. This is especially important if the behaviour may escalate or if termination becomes necessary.
Prepare for the conversation by clarifying your objectives. What specific behaviour needs to change? What does acceptable behaviour look like? What are the consequences if the behaviour does not change? Having clear answers to these questions makes the conversation more productive.
Having the Difficult Conversation
Be direct and specific. Describe the behaviour you have observed, explain its impact on the team, and set clear expectations for change. Avoid softening the message to the point where it is unclear. The person needs to understand that the behaviour is unacceptable and must change.
Listen to their perspective. Sometimes toxic behaviour has a root cause - overwhelming stress, personal problems, feeling unrecognised, or a mismatch between the role and their strengths. Understanding the cause can inform your approach to resolution, though it does not excuse the behaviour.
Set a clear timeline for improvement and define what success looks like. Follow up the conversation with a written summary so there is no ambiguity about expectations. Schedule regular check-ins to monitor progress and provide feedback.
Supporting the Rest of the Team
While respecting confidentiality about the specific conversation, acknowledge to the team that you are aware of the issues and are addressing them. Team members who have been affected by the toxic behaviour need to know that their concerns are being taken seriously.
Check in individually with people who have been most affected. Some may need support, reassurance, or simply the opportunity to express how the behaviour has impacted them. Validate their experience without sharing details of the corrective action.
When to Escalate or Terminate
If the behaviour does not improve after clear feedback and a reasonable improvement period, escalate to formal performance management. This typically involves a Performance Improvement Plan (PIP) with specific behavioural requirements, support resources, and a clear timeline.
Do not delay termination when it becomes necessary. Keeping a toxic team member who refuses to change signals to the rest of the team that the behaviour is tolerable. Every week of delay costs you the trust and engagement of the engineers who are suffering from the toxicity.
After the person leaves, invest in rebuilding the team's culture. The damage done by toxic behaviour can linger even after the source is removed. Facilitate open conversations about what the team wants their culture to be, and reinforce positive norms through your own behaviour and recognition.
Key Takeaways
- Distinguish between difficult personalities and genuinely toxic behaviour based on consistent negative impact
- Document specific behaviours with dates and exact examples before confronting the individual
- Have a direct conversation with clear expectations, a timeline for improvement, and consequences for non-compliance
- Support affected team members while respecting confidentiality about the corrective process
- Do not delay escalation or termination - keeping a toxic member damages the entire team
Frequently Asked Questions
- What if the toxic team member is also the team's best technical performer?
- No individual's technical output outweighs the damage of toxic behaviour. The productivity lost from demoralised teammates, departing engineers, and a culture of fear almost always exceeds the individual's contribution. Address the behaviour with the same standards you would apply to any team member. If they cannot work collaboratively, they cannot be effective on a team, regardless of their technical skill.
- How do I handle a team member who is toxic only to certain people?
- This is still toxic behaviour and should be addressed with equal seriousness. Targeted toxicity - whether based on seniority, gender, background, or personal relationships - is particularly damaging because it creates an unequal and hostile environment. Address it directly with specific examples and make clear that respectful treatment of all colleagues is non-negotiable.
- What if I inherited a toxic team member from a previous manager who tolerated the behaviour?
- You are not bound by your predecessor's management choices. Set your expectations clearly and give the individual a fair opportunity to adjust. Be explicit that things are changing: 'Under my management, I expect all team interactions to be respectful and constructive.' Provide specific feedback on any behaviour that does not meet this standard. The person deserves a chance to adapt, but the team deserves a healthy environment.
Explore Difficult Conversations Resources
Access our field guide resources on navigating difficult conversations, including scripts, frameworks, and follow-up strategies for engineering managers.
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