In this study, the bacterium Sphingomonas sphingomonas 503 was isolated from water samples. One ml of water sample was cultured on MH broth for enriching bacterial growth then subcultured on MH agar plates till obtaining pure separate deep yellow-pigmented colonies (after four subcultures). The bacteria were cultured on blood agar and chromogenic agar, giving white hemolytic and green colonies, respectively. The bacterial isolates showed Gram-negative, polymorphic rods without special arrangement. The bacteria was identified by the VITEK Compaq® 2 system as Sphingomonas paucimobilis 503  and assayed for antibiotic susceptibility using Ampicillin, Ampicillin/sulbactam, Piperacillin/tazobactam, Cefazolin, Ceftazidime, Ceftriaxone, Cefepime, Meropenem, Amikacin, Gentamycin, Tobramycin, Ciprofloxacin, Levofloxacin, Nitrofurantoin, Trimethoprim/Sulfamethazole. This bacterium was sensitive to all tested antibiotics except Ceftazidime, which showed the highest MIC ≥ 64, while the lowest MIC was that of  Levofloxacin ≤0.12and Ciprofloxacin ≤ 0.25