They give us unconditional love and companionship, but they also provide some important health benefits.
Mary Paula Henskath and her dog, Duncan, are regulars at Pastorous Park in the Chestnut Hill section of Philadelphia.
The pup is more than just a loyal companion.
"I was having a problem with arthritis and I was stiff and sore and I wasn't getting enough exercise so I purposefully got a very energetic dog," she explains.
And energetic he is.
Mary Paula says she walks Duncan three to four times a day.
It turns out he was the perfect remedy.
"It made me feel much better," she says. "I'm much stronger and have a lot less pain all because of Duncan."
Veterinarian Dr. Sheldon Gerstenfeld says animals can provide all kinds of health benefits.
"It lowers your blood pressure, lowers your cholesterol, it gives you a lot of exercise because you'll be walking your dog for example or your cat like I do," he says.
Dr. Gerstenfeld walks his cat, Daniel, 20 minutes a day just about every day, which he says is great for overall cardiovascular health.
The vet says just being outside in nature will do you a world of good as well.
"You can just go outside and just listen to the birds, look at the birds, take a chair outside and look at an ant society because this will be a stress reliever," he says.
If you are not an animal person, fish are an option.
A study out of the University of Pennsylvania showed that you can lower your blood pressure just by watching a fish tank.