Professor Barrett is Head of Fossil Vertebrates at the Natural History Museum, London, and the museum's public face for dinosaur-related discoveries. He is also President of the Palaeontographical Society. 

His research has several strands, but is centred on collections and field-based studies of dinosaur taxonomy, evolution, and palaeobiology, although he also works on other extinct reptile groups such as lizards and turtles. Current projects are concentrating on descriptions of new dinosaur species from Africa and South America, as well as detailed revisions of animals from China, the UK, Australia, and the USA.

Professor Barrett read Natural Sciences at Trinity College, Cambridge, and continued there with a PhD in Vertebrate Palaeontology (Herbivory in the non-avian Dinosauria) before moving to a fixed-term teaching post at Oxford University.