Purpose - This paper examines the issue of knowledge protection in Knowledge-Intensive Business Services (KIBS). This is a crucial question that has received little attention in the literature. Studies have mainly focused on traditional intellectual property protection methods, like those applied by large manufacturing firms, while little attention has been devoted to services companies. The paper aims at filling this gap by investigating knowledge protection methods adopted by KIBS companies. More precisely, it addresses the following research questions: a) do KIBS firms perceive the necessity to protect their knowledge? b) If so, do they protect it? c) What method (or combinations of methods) they typically use? d) What are the main factors affecting the approaches to knowledge protection that these companies adopt? Design/methodology/approach - The paper illustrates and discusses the findings of a survey of 471 KIBS companies located in the Northeast of Italy and operating in three different sectors (ICT Services, Design and Communication, Professional Services). In particular, the study: a) classifies the types of knowledge protection mechanisms used by companies; b) investigates similarities and differences in knowledge protection between KIBS operating in distinct sectors, having different size and pursuing specific service delivering strategies; c) analyses the relationship between the attitude of KIBS companies to interact with other companies and their need to protect their knowledge. Originality/value - The issue of knowledge protection is relatively new in the literature of KIBS. The state-of-the-art research shows that there are some important gaps that need to be filled. In particular, since the notion of knowledge as an economic resource is still ambiguous and difficult to handle, it is hard to define proper mechanisms of its protection. Thus, it appears important to explore the link between the characteristics of a KIBS company (in terms of delivered services, markets served, kind of external interactions, cognitive processes, etc.) and the adoption of protection mechanisms. Since KIBS companies are heterogeneous and so are the services they provide, the paper attempts to shed new light into the variety of issues and solutions adopted in different contexts or situations. Practical implications - The outcomes of the investigation can have important implications from a managerial viewpoint. In particular, the study can provide food for though to both CEOs of KIBS companies regarding the mechanisms of knowledge protection, and to policy-makers about the possible public policies that may help companies to protect their competitive knowledge capital without hindering their networks of interaction.