The present study was designed to investigate the antibacterial, cytotoxic and insecticidal activities of the methanol (85%) extract of barks of Hibiscus sabdariffa (MEHS). Antibacterial tests were done against six Gram-positive and eight Gram-negative bacteria using disc diffusion method. The extract showed the highest activity against Escherichia coli (14± 0.21 mm) followed by Shigella dysenteriae (13± 0.09), Sarcina lutea (13± 0.13mm), Shigella boydii (12± 0.12mm) and Staphylococcus aureus (12± 0.12mm) whereas inactive against Bacillus subtilis, B. megaterium, B. anthracis and B. cereus. The cytotoxic activities of crude extract was determined using Brine Shrimp lethality Bioassay and LC 50 values of standard Vincristine sulphate as a positive control and the crude extract were found to be 0.21±0.19µg/ml and 9.605±0.21µg/ml respectively. In insecticidal study, MEHS showed the significant activity with 100% mortality rate of Tribolium castaneum at a dose of 50mg/ml with 12 hours and also showed the activity in a dose dependent manner. INTRODUCTION Globalization interferes with infectious disease control at the national level while microbes move freely around the world, unrestricted by borders, human responses to infectious diseases and are conditioned by jurisdictional boundaries [1]. According to WHO, important progress has been made in controlling major infectious diseases. About 43% of total deaths occurred in developing countries due to infectious diseases in recent years [2]. Bangladesh, being a country with high density of population, infectious diseases becomes a great challenge in the health and economic sector. Multiple drug resistance has developed due to the indiscriminate use of commercial antimicrobial drugs commonly used in the treatment of infectious diseases. This results in the need of higher dose use with increased risk of drug toxicity or consideration to change the regimen. In addition to this problem, antibiotics are sometimes associated with adverse effects on the host including hypersensitivity, immune-suppression and allergic reactions. This situation force scientists to search for new antimicrobial substances. Similarly, freedom from insect invasion and contamination has become an important consideration in storage of grain and to maintain high quality food product by preventing them from attack of the most frequently invading organisms [3]. Nearly one thousand species of insects have been associated with store products throughout the world. Tribolium castaneum (Herbst) is considered to be a major pest of stored grains. In Bangladesh Tribolium castaneum is abundantly found in stored grains of different cereals. Control of these insects relies heavily on the use of synthetic insecticides and fumigants, which has led to problem such as disturbances of the environment, increasing cost of application, pest resurgence, resistant to pesticides and lethal effects on non-target organism in addition to direct toxicity to users [4]. So there is an immediate need to develop safe alternatives with low cost, easy to use and friendly to the environment. Various medicinal plants and plant products have been used for years in daily life to treat diseases all over the world. Medicinal plants are important source of traditional and synthetic medicines containing different types of organic compounds having therapeutic properties. In Bangladesh thousands of species