Ms. Goodfriend, 79, who started counseling pet owners in 2005, credited this spike to the pandemic, which she said made people “more aware of grief and more inclined to express it.”

At the Schwarzman Animal Medical Center, which has been operating in Manhattan since 1910, a free pet-loss-support group has been available to clients since 1983. Susan Cohen, 79, a veterinary social worker who came up with the idea for the group, said it started with about five people attending each in-person session. By the time she stopped working at the center, in 2011, that number had doubled.

The demand for such gatherings led the center to expand its offerings: There are now multiple grief groups that meet on video calls a few times a month. One is for people whose animals have died in the last three months, while another caters to owners still grieving pets who have died within the last year. Judith Harbour, 40, a veterinary social worker at the center who leads the grief groups, recently started a third for owners of dogs with serious health issues. Each group has 20 participants from across the country, and some have wait-lists.

Attendees come from a variety of backgrounds, Ms. Harbour said, and range in age from 18 to 85. The pets they’re mourning aren’t only cats and dogs — turtles, cockatiels, parrots, lizards, horses, and rabbits have been brought up in sessions, too, she said.

Ms. Harbour, whose job also entails daily counseling for individual clients and veterinarians at the center, said that many group attendees have said they felt unable to fully express their sadness over a dying pet with people close to them. Some have felt judged for grieving their pets, she said, while others have felt dismissed by loved ones who have told them to get another pet and move on.

She said the pain of a pet’s death often goes unrecognized by a person’s community and by society as a whole: “When you go through something like that you really feel unseen and you’re kind of on your own.”