Pine cones are not toxic to dogs, according to The Daily Puppy, but it is not a good idea to allow dogs to chew on them or eat them. Pine sap and pine needles are toxic to dogs, both of which may be present on pine cones.
Garden Guides advises that the sap and needles of the Australian pine contain an unknown substance that causes vomiting and depression when dogs and cats ingest it. The Daily Puppy explains that dogs who swallow pine cones risk intestinal perforations from the sharp points on the pine cones. Since pine cones are hard and not easily digested, ingestion can cause intestinal blockages.