His early career was as a theoretical ecologist but he now specialises in scientific research of biodiversity and conservation biology.

[9] Pimm has collaborated with a wide range of other scientists, including Robert May,[10] Peter H. Raven, Joel E. Cohen, George Sugihara, Thomas Loveloy, and Jared Diamond.

[25] A new wasp species from the cloud forests of Colombia's tropical Andes has been named Dolichomitus pimmi in honor of Pimm and his conservation efforts in that region.

[27][28] Saving Nature partners with local nonprofit organizations to connect fragmented habitats into biocorridors for wildlife.

[29] In 2014, Pimm was involved in a controversy related to allegedly sexist remarks he made in a book review[30] published by the Elsevier journal Biological Conservation.

"We would like to inform our readers that parts of the book review Keeping Wild: Against the Domestication of the Earth by Stuart Pimm, Volume 180, pages 151–152 are denigrating to women.".

In a later letter to the editor,[33] Amanda Stanley, then Conservation Science Program Officer at the Wilburforce Foundation, explained why Pimm's "...book review [was] so offensive.