The dried plant specimens painstakingly acquired by the London apothecary James Petiver (
ca
1663–1718) from around the world constitute a substantial, but underappreciated, component of the vast herbarium of Sir Hans Sloane, now housed at London's Natural History Museum. Petiver was an observant field biologist whose own collecting was focused in south-east England. However, he also obtained specimens from an astoundingly wide geographical area via numerous collectors, more than 160 of whose names are known. While many were wild-collected, gardens in Great Britain and abroad also played a role in facilitating the study of the many new and strange exotics that were arriving in Europe. A new estimate of the number of specimens present in Petiver's herbarium suggests a figure of
ca
21 000 gatherings. In this article, the appearance of the bound volumes, and the arrangement of the specimens within them, is assessed and contrasted with those volumes assembled by Leonard Plukenet and Hans Sloane. Petiver's published species descriptions and illustrations are shown to be frequently associated with extant specimens, letters and other manuscripts, making the whole a rich archive for the study of early modern collecting of natural curiosities at a time of increasing ‘scientific’ purpose.