The damping performance of a unidirectional (0 degrees) nylon 6-carbon fibre (NY-6/CF) commingled yam composite was experimentally studied with special concern for the effect of moisture absorption. Dried specimens were immersed in distilled water for a certain time to allow water to diffuse into the material. The damping measurements were conducted on double-cantilever and cantilever beam specimens using sinusoidal and impact-hammering techniques. The damping loss factor eta, flexural dynamic stiffness E’ and loss modulus E" were evaluated as a function of the moisture content up to 8.2 wt %, eta and E" initially increased significantly with increasing moisture content up to 5-6%. Further increase of the moisture content up to 8.2% caused a slight reduction in damping ability. The reverse was true of E’ although the variation amplitude was smaller. The moisture content dependency of the damping performance obtained is discussed.