Abstract: Sea cucumbers are potentially presented as the marine sources of antimicrobial and cytotoxic compounds. In this study, we focused on the sea cucumber, Holothuria leucospilota which has not been evaluated until now for antibacterial, antifungal and toxicity of its main organs. Ethyl acetate, methanol and water-methanol extracts were prepared from cuvierian organ, coelomic fluid and body wall of H. leucospilota collected from Persian Gulf. Extracts were evaluated for their antibacterial and antifungal activities against Aspergillus niger, Candida albicans, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. The activity was determined using the disc diffusion test. Cytotoxic activities of the extracts were assessed by Artemia salina larvae. Results showed that methanol extract of cuvierian organ (Minimum inhibitory concentration (MIC/disc) <1 mg against A. niger) and water-methanol extract of coelomic fluid (MIC/disc = 1 mg against C. albicans) showed significant antifungal activities but no inhibitory effect of the extracts against bacteria was observed. MIC for water-methanol extract of coelomic fluid was 3 mg against both C. albicans and A. niger. Significant inhibitory effect was observed in cytotoxic assays which was highest in body wall methanol extract (LC50 = 0.4 μg mL-1).