Large pupils in cats can happen for several reasons, and not all of them are cause for concern. In low light, their pupils naturally expand to let in more light, improving night vision. However, if the pupils remain dilated in bright conditions, it could indicate excitement, fear, or even playfulness—cats often have big pupils when they're highly stimulated. On the other hand, persistent dilation might signal health problems like hypertension, eye injury, or neurological issues. If your cat’s pupils don’t respond to light changes or are accompanied by other symptoms (squinting, lethargy), a vet visit is a good idea.