Tell me about a time you had to address a teammate's persistent underperformance.

How to answer this behavioral interview question: a complete STAR example, the mistakes interviewers watch for, and the follow-ups you should expect.

A strong STAR example answer

On my previous team, one engineer's work had become a liability. Over two months, his pull requests averaged four rounds of review, he had broken the staging build six times, and the rest of the five-person team was quietly absorbing his spillover — our sprint completion rate had fallen from 90 to 68 percent. As the tech lead, addressing it was my job, and I had been avoiding it because he was well liked.

I started by checking my own assumptions: I reviewed his tickets and found he was consistently assigned the most ambiguous work, which partly explained the failures — a resourcing mistake I had made. Then I had a direct, private conversation. I laid out the specific numbers, asked for his view, and listened. He revealed he was struggling with our new infrastructure stack and too embarrassed to ask for help.

We built a two-track plan: I rebalanced assignments so he owned a well-defined service area, paired him with our strongest infrastructure engineer for two sessions a week, and set a thirty-day check-in with clear quality bars. I also told the team I was handling it, without details, to stop the quiet resentment.

Within a month and a half his review cycles dropped to two rounds, sprint completion recovered to 88 percent, and he later became our on-call specialist. His one-on-ones went from the most guarded on the team to the most candid, which told me more than the metrics did.

How to structure your own answer

• Situation: Quantify the underperformance and its cost to the team.
• Task: Explain why addressing it was your responsibility.
• Action: Show how you checked your own contribution first, then had the direct conversation.
• Result: Give the measurable recovery and what it taught you about performance issues.

Common mistakes to avoid

• Going straight to the manager or HR without ever speaking to the teammate directly.
• Presenting vague complaints instead of concrete, measurable evidence of the problem.
• Skipping the step of checking whether your own processes contributed to the failure.
• Ending the story at the conversation with no follow-through plan or measurable recovery.

Follow-up questions to prepare for

Interviewers use follow-ups to verify your story is real. If you use this question in a real interview, expect probes like:

• What was your plan if the thirty-day check-in showed no improvement?
• How do you protect team morale while keeping the individual conversation confidential?
• Have you ever been the underperformer in a story like this?

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