Mastiffs can be good with cats, especially if they are raised together or properly introduced and socialized at an early age. Their calm and gentle nature can make them compatible with cats. However, due to their large size, supervision during initial interactions is advisable to ensure they don't accidentally harm the cat. Individual temperaments can vary, so it's important to consider the specific dog's personality and history with cats. With patience and proper training, Mastiffs can form strong, harmonious bonds with feline family members.