Some Vibrio strains are pathogenic and cause vibriosis, a serious infectious disease in maricultured organisms, and in recent years, Vibrio harveyi has been described to be pathogenic to children with cancer. Bioluminescent V. harveyi TEMO5 and TEMS1 were isolated from intestine contents of Holothuria tubulosa and seawater of Izmir Gulf (Turkey) for the first time. Hence, in this study, susceptibility patterns of 21 different antibiotics against these isolates were investigated by agar disc diffusion and micro-dilution method. The findings indicate that while these isolates were resistant to beta-lactam antibiotics (ampicillin, cephalothin and cephazolin) and very sensitive to aminoglycoside antibiotics (tobramycin and gentamicin), sulphamethoxazole/ trimethoprim and chloramphenicol, they were resistant to amoxicillin-clavulanic acid inhibiting beta-lactamases. Therefore, V. harveyi TEMO5 and TEMS1 are likely to acquire resistance by maintaining in response to natural environmental selection, or changing the permeability of outer membrane anion (porin) channels, or at chromosomal level.