Background: Endogenous interferences are an important source of biased laboratory results. Hemolysis, lipemia and icteria are the main source of endogenous interference in laboratory medicine. Accreditation according to ISO 15189 improves the overall quality of the laboratory procedures. The aim of our study was i) to assess the level of knowledge of Croatian medical biochemists about the proper detection and management of hemolysis, lipemia and icteria ; and ii) to identify possible differences in the level of knowledge respective to the laboratory accreditation status. Methods: An on-line self-report survey was carried out by the Working Group for Preanalytical Phase of the Croatian Society of Medical Biochemistry and Laboratory Medicine during April to May 2015. Survey included 14 statements (Q1–Q14) about procedures for samples with interferences and participants were asked to assess the degree of agreement with the statement using a 4-point Likert scale. Results: The lowest level of knowledge was observed for statements Q10 (dealing with icteric sample ; 40.9% participants agreed with the correct procedure), Q12 (allowable error for interference ; 47.2%) and Q11 (dealing with lipemic sample ; 60.1%). Almost all participants (97.4%) agreed that laboratories in Croatia should have a harmonized protocol for management of samples with interferences. Participants from accredited laboratories showed higher knowledge of hemolysis detection (p = 0.031), rejection of hemolyzed sample (p < 0.001), management of icteric samples (p = 0.038) and allowable error for interferences (p = 0.040). Conclusions: Croatian laboratories have a good knowledge of the proper detection and management of hemolyzed, icteric and lipemic samples. Accreditation is associated with higher knowledge about management of samples with interferences.