This study was undertaken to isolate the bacterial contaminants found on the Adult Monarch butterfly (Danaus plexippus) found on milkweed (Calotropis procera) in Jazan, Kingdom of Saudi Arabia. A total of 50 adult Danaus plexippus butterflies (n = 50) were obtained from Calotropis procera plant which is a common weed found in Saudi Arabia. The butterflies were caught and transported to the laboratory using sterile aseptic techniques. The butterflies were kept on sterile Nutrient agar and MacConkeys agar plates. The agar plates were incubated at 37°C for 24 hours and observed for growth. The colonies were subjected to Grams‟ staining and observed under a microscope. The isolates were identified using standard identification procedures. All 50 (100%) samples showed bacterial contamination. Gram negative bacilli, Pseudomonas aeruginosa was isolated form 37 (74%) samples and Gram positive bacilli, Bacillus thuringiensis was isolated from 27 (54%) samples. Mixed culture of bacteria were found on 14 (28%) of the samples. The presence of bacterial contaminants on adult Monarch butterfly indicated possible health hazard and a probable tool for the spread of microorganisms