WASHINGTON — Coronavirus cases are rising. President Biden’s domestic agenda is hanging in the balance. What better time to get a new puppy?

On Monday, the president introduced the newest four-legged resident of 1600 Pennsylvania Avenue: a German shepherd with very large, pointy ears. The 3-month-old canine is named Commander.

“Hey, pal,” Mr. Biden said to Commander, rubbing his head in a video posted to his Twitter account. “How you doing? How are you?”

In another shot from the upbeat video, a masked president and Jill Biden, the first lady, strolled into the White House with an eager-looking Commander pulling ahead on his leash.

The arrival of “the newest Biden,” as the president called Commander on Twitter, comes after the sad news in June that Champ, one of his two German shepherds, had died. Champ, who was 13, was mourned in a statement at the time by the Bidens.

“In our most joyful moments and in our most grief-stricken days, he was there with us, sensitive to our every unspoken feeling and emotion,” they said. “We love our sweet, good boy and will miss him always.”

Commander will continue the tradition of a canine presence at the White House. And White House officials said a cat — a female whose name has yet to be announced — will join the Bidens in January. In an interview this fall, Dr. Biden said that the cat had been living with a foster family and that she was uncertain that the caretakers would be willing to give up the animal.

As he adjusts to White House life, Commander will not have another dog to romp with.

The Bidens’ other German shepherd, Major, had been sent to training after a series of biting episodes in the East Wing. At the time, Michael LaRosa, Ms. Biden’s spokesman, described it as “some additional training to help him adjust to life in the White House.”

Now, Mr. LaRosa said Major would be living at another house.

“After consulting with dog trainers, animal behaviorists and veterinarians, the first family has decided to follow the experts’ collective recommendation that it would be safest for Major to live in a quieter environment with family friends,” Mr. LaRosa said in a statement. “This is not in reaction to any new or specific incident, but rather a decision reached after several months of deliberation as a family and discussions with experts.”

Commander was born on Sept. 1, making him by far the youngest Biden at the White House. The puppy was a gift from the president’s brother James Biden and sister-in-law Sara Biden. Commander arrived at the White House on Monday afternoon and could be seen romping through the grass outside.

In addition to the short video clip, Mr. Biden also tweeted a photograph of Commander, his big ears flopping as he ran with a green tennis ball in his mouth.

“Welcome to the White House, Commander,” the president wrote.