Hendrickson has found important fossils, artifacts, and shipwrecks around the world, including ancient fossilized whales in the Peruvian desert (with Kirby Siber), 24-million-year-old amber-encased butterflies and other insects in the Dominican Republic, ancient Egyptian and Napoleonic treasures sunken in the Alexandria River in Egypt, and Chinese porcelain and other treasures from a 400-year-old sunken Spanish galleon (the San Diego) off the coast of the Philippines (with Franck Goddio in 1992).

In 1990, Hendrickson was on a dinosaur dig in the Black Hills of South Dakota (the Badlands) with Peter Larsen, when she found the now-famous giant T. rex fossil. On August 12,1990, she was searching for fossils on a remote cliff with her golden retriever, Gypsy. After many hours, she noticed a few bones, and then some enormous dinosaur backbones. It took about three weeks to remove the huge bones from the cliff and years to clean the bones at the Field Museum.