Abstract: A survey on the incidence of Nosema bombycis infection on diamondback moth (DBM), Plutella xylostella (L.), was conducted in the cabbage fields of Cameron Highland (CH) and Serdang-Gombak (SG), each of them represent a high and lowland cabbage growing areas respectively, and laboratory culture of MARDI. Percent of Nosema infection (disease incidence) on the DBM larvae was much higher in CH (73.1%) than in SG (10%). The disease was prevalence in the highland cabbage fields or in low temperature environment. Although the percent of infection on DBM pupae showed a similar trend as for larvae, the difference was much smaller (13.3% and 8% in CH and SG respectively). This suggests that many infected DBM larvae in the CH had failed to develop and form DBM pupae. The infection intensity (number of spores per larva or pupa) and the range of infection intensity also showed similar trend as the percent of disease infection. More than 70 and 85% of DBM eggs and larvae, respectively, of the laboratory culture were infected by N. bombycis. The high percent of infection in the field population could be viewed as good news as N. bombycis may have a potential to be used as a biological control agent of DBM. But N. bombycis could indirectly kill parasitoid larvae within the infected DBM larvae of laboratory reared and field population. As such further study on impact of N. bombycis to DBM need to be conducted before any suggestion on it use can be made.