Spar platforms have several advantages for deploying wind turbines in offshore for depth beyond 120 m. The merit of spar platform is large range of topside payloads, favourable motions compared to other floating structures and minimum hull/deck interface. This paper addresses the effect of mooring line damages in responses of spar platform subjected to regular waves. A 1:100 scale model of the spar with taut (intact), taut (damaged) and slack (intact) mooring line configuration was studied in the wave basin (30 × 30 × 3 m) in Ocean Engineering Department of IIT Madras. The heave and surge accelerations along with mooring line tension was measured and used. The surge and heave RAO comparison for all three mooring line conditions shows that the effect of damaged mooring line in surge response is negligible whereas in heave response, taut (damaged) will behave similar to slack (intact) condition. The normalized mooring line tension comparison between taut intact and taut damaged configuration is also presented. © 2012, The Institution of Engineers (India).