What should I do about a high-performing engineer who is toxic to the team?

One engineer delivers strong results but undermines others, causing tension and reduced team cohesion.

Treat this as a performance issue, not a personality quirk. Impact on the team is part of the role, especially at senior levels. If someones output is high but their behaviour reduces the output of others, the net effect is negative.

Be specific about the behaviours and their impact. Avoid labels like toxic and instead describe what happens: interrupting others, dismissing ideas, creating reluctance to speak up. Then connect it to outcomes: slower decisions, reduced collaboration, lower morale.

Reset expectations clearly. High performance includes how work gets done, not just what gets delivered. Make it explicit that collaboration and psychological safety are non-negotiable.

Give them a chance to adjust with clear examples of what good looks like. If theyre capable, theyll adapt. If they push back or minimise, thats useful data.

Follow through. If behaviour doesnt change, youre choosing to tolerate the impact on the wider team.

• Document specific behaviours and their impact
• Have a direct conversation focused on outcomes, not personality
• Define clear behavioural expectations
• Agree what improvement looks like over the next few weeks
• Monitor team dynamics, not just individual output

Protecting the individual because they deliver results  while the rest of the team quietly disengages.

Helps you prepare the conversation with clear examples, track behavioural commitments, and reflect on team impact over time rather than relying on instinct.