Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are implicated in the development of several diseases but the contribution of each of the species is yet to be fully established. EDTA and citrate as anticoagulants chelate calcium, which is integral to coagulation mechanism. Whether these chelating agents as well as the different coagulation pathways are differently associated with nitrosative and oxidative stress has also yet to be fully elucidated. This preliminary study investigated the possible correlations between the levels of indices of RNS and ROS in blood and in blood-clotting using EDTA- and citrate -anticoagulated blood. Thirty blood samples from sheep were collected into EDTA and citrate tubes at the Berrima Veterinary Laboratory using their standard protocol. Nitrosative and oxidative stress indices were measured and correlation analyses were performed. Regardless of anticoagulant use, none of the nitrosative or oxidative biomarkers was significantly associated with changes in the prothrombin time. The activated partial thromboplastin time showed statistically significant association with some oxidative stress indices (catalase and MDA), but with none of the nitrosative stress indices. The biomarkers were more correlated and statistically significantly associated with others from the EDTA sample compared to citrated blood. Further, all measured parameters were higher in EDTA than in citrate, although GSH and MDA did not achieve statistical significance. Perhaps the suggestion that EDTA is better than citrate for haematological anticoagulant studies should be seriously considered when validating nitrosative and oxidative stress tests