Though the impact of parasitic infections on giant freshwater prawn Macrobrachium rosenbergii is generally regarded low, there are new diseases being reported recently. As more M. rosenbergii fry are entering the country from Thailand, monitoring of their health status needs to be tightened to prevent disease occurrence. Screening of parasitic infestation on M. rosenbergii was carried out since 2007: cultured samples taken from 2 states (Kedah and Negeri Sembilan) and wild samples from one state (Perak). The study showed symptom of black spots/patches on the rostrum, carapace, pleopod or telson in most of the prawn samples (average body weight: 52.67g). Prevalence of 100% of this symptom was seen in Kedah and Negeri Sembilan samples while 18.37% were recorded for Perak sample. Parasitic examination revealed protozoa infection (Zoothamnium sp. and Vorticella sp.) with prevalence of 100% (n=91), 75% (n=34) and 69.39% (n=49) from Kedah, Perak and Negeri Sembilan samples respectively. Nematopsis sp. (A gegarine of protozoan) with a prevalence of 68.75% was found in wild samples from Perak. Infection of leech cocoon was seen in most of Kedah samples with a prevalence of 21.97% and a mean intensity of cocoon per prawn was 45.55. In Perak, a higher prevalence of 35.8% with a mean intensity of 139.30 per prawn was recorded. However, no infection of leech cocoon was seen from cultured prawn from Negeri Sembilan.