Sometimes — with care
Yes, the flesh is safe — most dogs just don’t love citrus. Peel, pith and seeds should be removed, and the sugar means small portions only.
Orange segments are non-toxic and provide vitamin C, potassium and fibre (though healthy dogs synthesise their own vitamin C). Many dogs wrinkle their nose at citrus oils and refuse anyway. The peel and white pith are hard to digest and concentrate citrus oils that can upset stomachs; seeds add trace bitter compounds. Citrus-flavoured products and essential oils are a separate, stronger irritant — keep those away from pets entirely.
One or two segments for a small dog, up to half an orange for a big dog, occasionally. Diabetic or overweight dogs should skip citrus — the sugar adds up. If your dog eats a dropped whole orange including peel, expect possible vomiting or loose stool and call the vet if it persists.
Dogs usually prefer mango, strawberries or watermelon for fruity treats.
This article is general information, not veterinary advice. If your pet has eaten something potentially harmful or shows symptoms, contact your vet or an emergency clinic immediately. Full disclaimer.