Success of a baculovirus in the field depends on the selection and utilization of effective isolates of viruses with increased pathogenicity and virulence. Isolates ofPlutella xylostella granuloviruses collected from Kenya and India were compared for genetic variations by restriction endonuclease enzyme analysis and for biological activity based on their median lethal concentration and time-to-kill early- and late-third instars. TheP. xylostella granulovirus isolates in Kenya were more diverse than those in India and were considerably different from the latter, with only 53–61% similarity. The Kenyan and Indian isolates did not differ significantly for their median lethal concentration, but the Kenyan isolate collected from Kibwezi was significantly faster than other isolates in killing early- and late-third instarP. xylostella. Cluster analysis of restriction fragment marker profiles of theP. xylostella granulovirus with other granuloviruses revealed that it grouped into a cluster with Spodoptera litura granulovirus, whereasHelicoverpa armigera andChilo infuscatellus granuloviruses grouped into another cluster. Results of the present study indicate the existence of genetically and biologically diverse isolates ofP. xylostella granulovirus which could be further developed into effective biopesticides for the management of diamondback moth.