A novel cathepsin B inhibitor-producing bacterium was isolated from marine sediments and identified based on its 16S rDNA sequence as Pseudomonas sp. strain PB01 (Accession No. EU126129). The growth and enzyme inhibitor production were investigated under various culture conditions. A mixture of organic nitrogen source was required for the optimal production, whereas both glucose and maltose proved to be the effective carbon sources for cathepsin B inhibitor production. Other optimal culture conditions included temperature range between 25 and $28^{circ}C$, initial medium pH of 6.6, and shaking speed of 200 rpm. Under these optimal conditions, the maximum inhibitory activity from culture broth was approximately 50% after 30 h of cultivation. Additionally, kinetic study revealed that inhibitor production paralleled with cell growth, which suggested that the inhibitor may be a primary metabolite of that bacterium.