The article discusses the protection of personal data of an expert witness in criminal proceedings. Due to the fact that the role of an expert witness is highly relevant to the outcome of the proceedings, the article discusses the measures for personal data protection granted to these entities in criminal proceedings. Since the release or disclosure of such personal data in criminal proceedings may pose a danger to expert witnesses, they receive special protection. Expert witnesses may also be additionally protected by other provisions or institutions protecting other entities and, incidentally, covering expert witnesses’ data protection.