When a Teammate Is Struggling: How to Recognize and Address Toxic Behavior on Software Teams
Most teams will encounter it at some point. A team member who consistently undermines colleagues, claims credit for others’ work, shuts down ideas in meetings, or creates an atmosphere where people stop speaking up. The instinct is to label that person toxic and figure out how to remove them.
Simon Sinek would stop you there.
In “Leaders Eat Last,” Sinek makes a point that organizations rarely want to hear: people almost never behave destructively in environments that make them feel safe and valued. When someone exhibits what we call toxic behavior, it is worth asking what conditions produced it before concluding anything about the person. That question does not excuse the behavior. It just leads to better outcomes than skipping straight to exit plans.
What Toxic Behavior Actually Looks Like
Before anything else, name it precisely. Vague labels get in the way. Specific behaviors are actionable.
The patterns that genuinely damage team health include credit-stealing without acknowledgment, persistent negativity that blocks forward momentum without offering alternatives, gossiping that creates divisions within the team, public undermining of colleagues or their work, refusal to share knowledge in ways that make the team dependent on one person, and consistent disregard for team decisions after they’ve been made.
Notice that this list is about behavior, not personality. Someone can be blunt, introverted, opinionated, or difficult to read and still be a healthy team member. The line is crossed when behavior consistently makes it harder for others to do their best work. That is what matters.
Why It Happens: The Safety Hypothesis
Google’s Project Aristotle, one of the most rigorous studies of team performance ever conducted, found that the single biggest predictor of an effective team was psychological safety. Amy Edmondson at Harvard describes it as a shared belief that the team is safe for interpersonal risk-taking. When it is present, people speak up, share uncertainty, and try things. When it is absent, people protect themselves.
Protective behavior can look like toxic behavior from the outside. Someone who attacks ideas before they can be dismissed is often someone who has experienced dismissal. Someone who hoards knowledge may have learned that knowledge is leverage because contribution is not recognized. Someone who undermines colleagues publicly might be operating in an environment where visible dominance is the only path to influence.
None of this makes the behavior acceptable. But it changes the intervention. You cannot fix a behavior that emerges from a system problem by treating it as a personal failing.
How to Address It: Start With Curiosity
The first step is a private conversation. Not a performance review framing, not an HR-adjacent tone, just a genuine one-on-one driven by curiosity.
Patrick Lencioni’s work on team trust suggests that vulnerability has to come from somewhere in the team first. If you are the team lead, model it. “I want to talk about something I observed and I genuinely want to understand your perspective on it.” Describe the specific behavior and its impact on the team, without attributing intent. “In last Tuesday’s review, when you said X, I noticed two people stop contributing to the conversation. I do not know what was happening for you, but I wanted to surface that.”
Then listen. Actually listen. Do not prepare your counter-argument while the other person speaks. Sinek is clear that leaders who make people feel heard before making decisions build trust that becomes the foundation of everything else.
That conversation will sometimes reveal something you did not know. A conflict with someone on the team you were unaware of. A feeling of being sidelined on decisions that affects this person’s area. Personal circumstances. None of those things are your problem to solve for them, but they change how you proceed.
Building the Culture That Prevents It
The most effective approach to toxic behavior is a team environment where it rarely takes root.
Sinek’s Circle of Safety is the framework. When people inside a team feel genuinely protected from external threats, competition, and unpredictability by the people around them, they can focus energy outward on the actual work. When they do not feel safe, they spend energy on internal politics and self-protection instead.
Practically, this means rituals that make it normal to share uncertainty. A team lead who says “I do not know, let us figure it out together” in a sprint planning session sets a precedent. A blameless postmortem process signals that mistakes are learning events rather than career risks. Recognition that is specific and public, not formulaic, tells people that contribution is actually seen.
Psychological safety is not softness. The teams with the highest psychological safety are also the ones that surface problems earliest, deliver feedback most directly, and hold each other most accountable. Safety creates the conditions for honest conversation, which is exactly what high performance requires.
When the Situation Requires Escalation
There are situations where empathy and conversation are not enough. Persistent behavior that continues after clear, documented feedback. Behavior that crosses into harassment or creates legal risk. Situations where one person’s presence is demonstrably degrading the performance or wellbeing of the rest of the team.
At that point, the conversation moves to HR and leadership, and it should. Document specific behaviors with dates. Be clear about what feedback was given and what changed or did not change. Approach it as a problem to solve for the team, not as a campaign against a person.
Even here, Sinek’s framing applies. The goal is a healthy team. Sometimes that means a person moves on. The way you handle that transition, the respect you show, and the message it sends to everyone watching matters for your culture long after the specific person has left.
The Takeaway for Software Teams
Toxic behavior damages psychological safety, which is the top predictor of team performance. Address the behavior, not the person. Start with curiosity before judgment. Build the kind of environment where people do not need to protect themselves from their teammates.
The teams that do this well do not eliminate conflict. They create conditions where conflict surfaces early and gets resolved rather than calcifying into something that corrodes from the inside out.