Direct oral anticoagulants (DOACs) have been increasingly used in the recent years for the prevention and treatment of thromboembolic disease. Due to their predictable pharmacokinetics, DOAC drug therapy is performed in fixed doses and does not require routine laboratory monitoring. On the other hand, due to their direct inhibitory effect on the activity of a certain segment of the haemostatic system, DOACs have a significant impact on the results of numerous haemostasis assays, both screening and specific. Understanding the influence of DOACs on a particular haemostasis assay is extremely important for correct interpretation of the results, as well as prevention of false positive or false negative results that could have a negative impact on the patient treatment. The aim of this study was to examine the effect of three DOACs, dabigatran, rivaroxaban and apixaban, on the results of routine screening haemostasis tests; PV, APTV, TV and fibrinogen. In the samples of patients treated with DOACs, dabigatran (n = 248), rivaroxaban (n = 294) and apixaban (n = 142), peak (2 hours after administration of the last dose) and trough concentrations (shortly before taking the next dose) of a certain DOAC were determined and screening haemostasis tests, PV, APTV, TV and fibrinogen, were conducted. The results of the conducted study showed that DOACs affect the results of haemostasis screening tests. This effect differs significantly depending on the type of DOAC used and the time of blood sampling in relation to the time of the administration of the last dose. The influence of DOACs on these assays is significantly larger at peak plasma concentrations of the drug when compared to the trough drug concentration. Dabigatran significantly affects TV and APTV test results and to a lesser extent PV, whilst it has no effect on fibrinogen assay. Rivaroxaban affects PV and APTV, but only at peak drug concentrations and has no effect on TV and fibrinogen. Apixaban has the lowest effect on the results of haemostasis screening tests, and the obtained values of all examined samples were within the reference interval at both peak and trough drug concentrations. This study indicates that haemostasis screening tests are not suitable for assessment of the anticoagulant effect and/or the concentration of a certain DOAC, whereas understanding the impact of DOACs on individual screening tests is essential for proper interpretation of obtained test results in everyday laboratory and clinical practice.