Captivity can induce high levels of stress in zoo animals, leading to health and behavioral problems that hamper conservation efforts, reduce the effectiveness of education, and negatively affect animal welfare. Zoos employ environmental enrichment to mitigate stress, but the effectiveness of various types of enrichment is poorly understood. We surveyed enrichment practices at 39 zoos nationwide and then used noninvasive fecal hormone analyses to monitor stress in three species of felids under different enrichment programs at two zoos. Baseline analyses at the National Zoological Park showed individual differences in stress hormone levels but no seasonal effects. Contrary to expectations, a novel enrichment program at Plumpton Park Zoo produced higher cortisol levels than a reduced enrichment program. Results suggest that novel objects that elicit active engagement may cause transient increases in stress hormones. Further long-term study is needed to elucidate whether this has a positive or negative effect on well-being.