Roxithromycin is a second‐generation macrolide antibiotic derived from erythromycin. In the current study, roxithromycin (ROX) was successfully labeled with technetium‐99m for early diagnosis of bacterial infection and discrimination between septic and aseptic inflammation. The highest radiochemical purity of ≥95% was achieved by investigating different labeling parameters such as pH, ligand/reducing agent concentration, temperature, and amount of stabilizing agent. For this purpose, 0.3–0.5 mg ligand, 2–6 μg SnCl2·2H2O as a reducing agent at basic pH (8–10 pH) and 2 mg mannitol used as a stabilizing agent, in the end, 370 MBq 99mTc added into the reaction vials and incubated for a wide range of temperature (−4 to 65°C). The percent radiochemical purity of 99mTc‐roxithromycin was assessed with the help of the radio‐thin‐layer chromatography technique. The characterization studies were carried out using electrophoresis and Radio‐HPLC techniques as well as saline stability and serum stability studies were also performed. Furthermore, biodistribution study was also performed in an inflamed animal model to discriminate between septic (heat‐killed Staphylococcus aureus) and aseptic (turpentine oil) inflammatory lesions. The results were elaborated that 99mTc‐roxithromycin (99mTc‐ROX) was clearly bounded at the septic inflammation site (T/NT ratio of 7.08 ± 1.14) at 30 min postadministration, and maximum accumulation was seen in heart, lungs, liver, stomach, kidneys, and intestine. The results were suggested that 99mTc‐ROX might be used to discriminate between septic and aseptic inflammatory lesions at an early stage.