The physiological mechanisms underlying the 'cost of reproduction' remain under debate, though oxidative stress has emerged as a potential candidate. The 'oxidative cost of reproduction' has received considerable attention with regards to food and antioxidant availability; however, the limitation of water availability has thus far been neglected. In this study, we experimentally examined the combined effect of pregnancy and water deprivation on oxidative status in a viviparous snake (Vipera aspis), a species naturally exposed to periods of water and food deprivation. We predicted a cumulative effect of pregnancy and dehydration on oxidative stress levels. Our results support the occurrence of an oxidative cost of reproduction as we found higher oxidative damage levels in pregnant females than in non-reproductive individuals, despite an upregulation of antioxidant defences. Surprisingly, water deprivation was associated with an up-regulation of antioxidant defences, and did not increase oxidative damage, either alone or in combination with reproduction.