Individuals in a population respond differently to stressful situations. While resilient individuals recover efficiently, others are susceptible to the same stressors. However, it remains challenging to identify resilience in mammalian embryos to determine if stress resilience is established as a trait during development or acquired later in life. Using a new behavioural paradigm in zebrafish larvae we revealed that resilience is established as a stable trait early during development, and that neuropeptides and the innate immune factors play positive and negative roles in determining resilience respectively.