Surface modifications of coir fibres involving alkali treatment, bleaching, and vinyl grafting are made in view of their use as reinforcing agents in general-purpose polyester resin matrix. The mechanical properties of composites like tensile, flexural and impact strength increase as a result of surface modification. Among all modifications, bleached (65°C) coir-polyester composites show better flexural strength (61.6 MPa) whereas 2% alkali-treated coir/polyester composites show significant improvement in tensile strength (26.80 MPa). Hybrid composites comprising glass fibre mat (7 wt.%), coir fibre mat (13 wt.%) and polyester resin matrix are prepared. Hybrid composites containing surface modified coir fibres show significant improvement in flexural strength. Water absorption studies of coir/polyester and hybrid composites show significant reduction in water absorption due to surface modifications of coir fibres. Scanning electron microscopy (SEM) investigations show that surface modifications improve the fibre/matrix adhesion.