In this study, in situ monitoring of single lap joint of woven glass fabric reinforced epoxy composites modified with multi-walled carbon nanotubes (MWCNTs) is presented. Woven glass fibre reinforced/epoxy composite plates modified with 3% wt. highly electrically conductive MWCNTs were manufactured by hand lay-up process for obtaining adherends. MWCNTs were used in 1% and 2% by weight in order to investigate the effect of the MWCNTs level on the shear lap joint strength and the self-sensing sensitivity of bonded area. One, four, and seven plies of adhesive woven cloths were employed for bonding adherends to examine the thickness effect on both the shear lap joint strength and the self-sensing sensitivity of bonded area. In order to provide low electrical contact resistance, woven carbon fibres were placed on the top and bottom of the glass fibre layer during production. Results indicate that the health monitoring of lap joints in the woven glass reinforced epoxy composites can be successfully achieved.