The site also includes discussion boards, a resource library and classified ads.

Petfinder.com is sponsorship supported and free to potential adopters and to its members.

Betsy Banks Saul and Jared Saul came up with the idea of Petfinder.com in early 1996 as a resolution to do something for homeless animals. They were not active in the animal sheltering community, but had skills with computers and graphic design. Overriding that, was a strong interest in animals. At first, the site was limited to their home state of New Jersey and was simply a labor of love. Demand and popularity led to rapid national and international expansion. Petfinder has always been a free service for shelters and rescue groups as well as potential adopters.

Petfinder is credited for changing the way Americans look for new pets. By Petfinder's 10th anniversary, it had helped place over 10,000,000 pets with families. Petfinder also created the first large-scale opportunity for North American companies to market to potential adopters allowing corporate advertising dollars to support the companies costs, and as such, flow into the resource-poor world of companion animal welfare. Original corporate sponsors were Petopia, Petco, Purina, Bissell, and Merial. Petfinder would sometimes host summits and bring these companies together to develop ideas to best promote homeless pets.

On November 2, 2006, Discovery Communications announced the acquisition of Petfinder.com. Betsy Banks Saul, petfinder.com's president and co-founder initially reported to Maureen Smith under Animal Planet Media Enterprises. Petfinder was later moved out of Animal Planet and into Discovery Communications' digital media group where it currently resides. Betsy Banks Saul and Jared Saul are still involved with Petfinder as are many of Petfinder's original employees. They are also founding board members of the Petfinder.com Foundation, which partners with Petfinder, Discovery Communications, for charitable causes.

The success of Petfinder has spurred the creation of many competitive sites such as shelternetwork, pets911, adoptapet.com and petango.com. Another charity that is somewhat linked to pet finder is Save-A-Sato. Which flies Puerto Rican dogs to the United States for adoption. Many of these dogs, such as Natalia the Terrier have happy endings from this organization.

At this time, Petfinder.com is responsible for finding homes for approximately 2.3 million pets each year.

In the wake of Hurricane Katrina, Petfinder.com served a vital role in reuniting displaced residents with the pets they were forced to leave behind. Animal welfare groups converged on the city of New Orleans, the flooded parishes, and the Gulf Coast to save hundreds of abandoned pets. As a voluntary project Petfinder.com and staff created the Animal Emergency Rescue Network, where over 17,000 pets were eventually posted.

Shelter and rescue groups across America, a self-appointed group of animal advocates called "the rogue volunteers" and Petfinder played a pivotal role in re-homing pets during Hurricane Katrina and through the emergency database Petfinder built, over 11,000 of the 17,000 lost and displaced pets were reunited with their original owners. Some of these reunions happened years after the hurricane.

Several non-profit organizations such as the Petfinder.com Foundation and Maddie's Fund helped support the Animal Emergency Rescue Network.