Due to enhanced mechanical strength, superior flame-resistance, decreased gas permeability, montmorillonite nano-clay has been introduced to the jute-polyester resin composite materials for structural application. Long fiber Bangla special tossa jute is being used as reinforcement materials along with 0%, 1%, 3% and 5% addition of nano-clay within the matrix-fiber mixture. Thermal behaviours of this jute composite were studied via dynamic mechanical analysis, thermogravimetric analysis and differential scanning calorimetry. The doped hand lay-up processed (32 cm×32 cm×3 mm) plates are used to make samples for dynamic mechanical analysis (50 mm × 12.7 mm × 3 mm) and thermogravimetry (6.75mg to 6.85mg) testing as per ASTM standards. Temperature induced weight loss due to Thermal decomposition were measured and char residue were calculated up to 1000ºC where 5% added nano clay samples showed better thermal stability. Viscoelastic properties through storage modulous and loss modulus showed better stability with 1% nanoclay added composite in dynamic mechanical analysis.Moisture and temperature did not affect the tested samples significantly in diminutive exposure for 1% nano clay
added samples even though there is a loss of storage modulus of 12 to 30% for 3% and 5% nanoclay added samples,respectively. Effect of temperature and high humidity were evaluated for this nano-clay filled composite through the hydrothermal test for 15 days in the environmental chamber. Environmental degradation was not remarkable due to the
exposure of the temperature 80ºC and 95% RH for this time period.