Oranda goldfish is an ornamental fish that developed worldwide. This industry faces serious problems such as Aeromonas salmonicida infection (furunculosis). Alternative therapy is required to be developed. One of them is using desert rose (Adenium obesum (Forssk.) Roem. & Schult.). This study aimed to elucidate the potency of desert rose flower extract (DRFE) against artificially induced furunculosis in oranda goldfish. The desert rose was extracted and its quercetin content was analyzed. Sixty oranda goldfish were used as a model. Fish were separated into I (healthy); II (infected); III (infected + 55 ppm ciprofloxacin); IV (infected + 1,000 ppm DRFE); V (infected + 2,000 ppm DRFE); VI (infected + 4,000 ppm DRFE). The therapy was given 5-days. On day six, the fish's blood and organs were collected. The samples were tested against haematology, histopathology, and immunohistochemistry. The data were analyzed by SPSS26. The results showed that DRFE contained quercetin (5.32±0.18%). The DRFE has potential benefits as healing promoters against furunculosis in oranda goldfish. It is indicated by significant differences in parameters: erythrocytes, haemoglobin, PCV, erythrocyte indices, leucocytes, differential leucocytes, histopathology, serology, and immune-expression of CD4+, CD8+, and ratio CD4+/CD8+ compared to the infected group (P≤0.05). The most significant concentration of DRFE was 4,000 ppm and it has no differences compared to 55 ppm ciprofloxacin (P≥0.05). The DRFE can be used as the alternative treatment against artificially induced furunculosis in oranda goldfish and it must be explored further against another type of bacterial infection.