How long does it take a Bullmastiff to be fully grown?
It is important to grow your Bullmastiff slowly. Your Bullmastiff can take three or more years to mature, being a lot slower than many other breeds in their physical and mental development. Keep your dog slim, prevent jumping and restrict exercise to puppy play ONLY until at least 12 months of age to enable joints and bones to grow strong and stable in their own time. The adolescent period can seem very long, but like human teenagers, they will come out the other side as well adjusted and well behaved adults if you apply patience, perseverance and consistency in managing their behaviour.