Stress is a pervasive welfare problem in domestic cats, manifest through behavioural, physiological, and health outcomes. Feline idiopathic cystitis (FIC) - a leading cause of emergency veterinary presentation - is stress-triggered in the majority of cases, demonstrating the direct welfare-health link. Stress indicators in cats include hiding, reduced grooming or over-grooming, house soiling, reduced feeding, and increased aggression. Multi-cat households, indoor-only confinement, inappropriate litter provision, and resource competition are primary stressors. The Cat Stress Score (CSS) and Feline Grimace Scale enable standardised welfare assessment. Environmental modification following cat-friendly practice principles (vertical space, multiple resources, predictable routines, choice and control) significantly reduces stress indicators. Research demonstrates that indoor cats provided with adequate environmental enrichment show cortisol levels comparable to outdoor cats. Feline synthetic pheromone products (Feliway) provide adjunct stress reduction in clinical settings.