While some owners use the site to let their friends and family members know about their new pet, others use it to further their pet's career in show business.
One such pet owner is Jeff Simmons, a 45-year-old communications manager from Queens and former spokesman for Controller Bill Thompson, who posts Facebook status updates for his dog, Bruno.
"People love to talk about their dogs," the New York Daily News quoted him as saying.
Simmons and his partner, Alfonso Quiroz, a 37-year-old Con Edison media relations rep, decided when they got their Brussels Griffon about a year ago that Facebook was a great way to let their friends and family know about their new pet.
"As relatively new dog owners, we wanted to share a big chapter in our lives with others," Simmons said.
Bruno the Brussels has nearly 500 friends on Facebook - more than most people.
"He's got a loyal following in our building and in our neighbourhood," Simmons revealed.
Erica Miolla, a 26-year-old Manhattan investment banker who lives in Manalapan, N.J., set up a Facebook page for her Yorkshire terrier, Rocky, about two years ago and he updates his status nearly every day.
"I thought it was cute. I wanted to show him off to my friends," she said.
"Most of the time it's, 'I'm waiting for my mom to get home from work'. He's not trained very well, so sometimes it's, 'I'm mad at my mom for leaving me, so I left her a present on the staircase'," she said with a laugh.
Miolla admits it's silly to have a Facebook page for her pet, but it makes her happy nonetheless.
"It's one of those feel-good things. Everyone loves it," she added.
Jenny Pulidore's cat, Molly, became famous four years ago when she was trapped for two weeks between the walls of Pulidore's father's deli in the West Village.
"I got the idea of putting up a page for Molly because at least twice a week since this whole fiasco happened, we get either a call or a customer coming in asking, 'How is she doing?'" Pulidore explained.
Pulidore doesn't update Molly's status as much as she'd like to, despite having some very special followers, like Kevin Clifford, who is one of Molly's rescuers, who stays in touch with the cat via Facebook.
"How's my pain in the butt kitty doing???" Clifford recently wrote on the cat's page.
Beth Joy Knutson, a 34-year-old comedian/animal activist from Manhattan, uses Facebook to help further her dog's career in show business.
"She Tweets, too," Knutson said of Bella, a mutt who has appeared in commercials.
"She's the digital-age dog," she added.