A study was conducted to determine the effects of subzero temperatures, seawater immersion and low velocity impact on the flexural strength, stiffness and life of sandwich composites. The study utilized 25.4mm wide specimens comprised of a 12.7mm thick Diab H100 core and eight-ply glass/vinylester face sheets with [0/90] 2s stacking sequences. Specimens were tested statically and in fatigue using a four-point bending arrangement that included a combined metal and rubber load pad that spanned the inner loading heads and which prevented any local crushing damage. Both undamaged and impact damaged specimens were tested in room temperature dry, room temperature seawater saturated, -20°C dry and -20°C seawater saturated environments. The impact damage level was 10J and was induced via a 25mm diameter, cylindrically shaped head that impacted the specimen across its full width. The primary results were that reducing the temperature tended to increase stiffness, strength and fatigue life. Seawater saturation had minimal effects on strength, stiffness or life, but influenced the static failure mode. Impact damage had little effect on the static results, but caused a significant loss in fatigue life. These results demonstrate that static test results cannot be used to infer fatigue behaviors, and indicate the need for the accurate determination of material and structural responses across the full range of expected usage environments.