Yes,BlackBerries can be eaten by dogs, they are a good treat for pets like dogs
Dogs can eat 2 to 3 blackberries a day.
Dogs should not be given berries like cherries, holly berries, juniper berries,
Dogs can eat strawberries but not in huge amounts or on a daily basis as it contain toxic material for dogs if feed in huge amount.
Blackberries and raspberries contain some or little amounts of naturally occurring xylitol
Blackberries should be first properly washed with clean water, it's better to give blackberries to your dog in a small amounts.
Blackberry juice is a good treat for dogs but does not add sugar or any sweetness in it.