Start with health and safety
Before close contact, consider veterinary examination, vaccination status, parasite control, and testing appropriate to species and history. Use separate food, water, resting areas, and litter boxes while the animals acclimate.
Scent before direct contact
Exchange bedding or use controlled scent exposure so each animal can investigate the other without pressure. Reward calm behavior. For cats, feeding on opposite sides of a closed door can build a positive association if neither animal is too stressed to eat.
Move slowly to visual contact
Baby gates, cracked doors, leashes, or other barriers can allow controlled viewing. End sessions before tension escalates. Hissing, growling, avoidance, freezing, stalking, or inability to disengage are signals to slow down.
Resource competition matters
Provide multiple separated resources. For multi-cat homes, litter boxes, food, water, resting sites, scratching areas, and vertical space should not all be concentrated in one location. Dogs may need separate feeding and high-value chew management.