Home / Dogs / Puppy in the home Puppy Matures (Between one and four years) No matter how much you wish your pup stay small, he'll certainly grow up. The dog becomes adult between one and four years. During this period serious changes in physical and psyche sphere take place and it is very important for a master to let his dog know his place. In short, while maturing, a puppy tends to become a leader, tries to impose his will on you, while the things should be the contrary. Virtually this is a common event, but you must unambiguously make him know who is the leader and who is the subordinate.