Purpose The purpose of this paper is to report the possible impact of intellectual capital (IC) on firm reputation (FR) and investigates if there is a relationship between FR and market internationalization (MI). Design/methodology/approach The data were collected from engineering consultancy firms (ECFs) in Turkey. The study employed structural equation modeling to examine the hypothesized relationships between IC, FR, and MI of ECFs. Findings ECFs with strong human and structural capital can have a good FR. However, healthy relational capital may not lead to the same effect on FR. On the contrary, FR can create high-quality relational capital for ECFs. Lastly, a good FR, based on robust human and structural capital, can provide the success of ECFs’ MI process. Research limitations/implications This model may be analyzed for other knowledge-intensive business services. Also, subsequent researches may investigate potential variations in results about other sectors and geographical areas. Moreover, various constructs may be included in the model. However, a greater number of samples could lead to distinctive outcomes. Practical implications The research may be a general guide for related professionals and their companies to build long-term strategies, given IC, FR and MI. In this respect, they should take into account human and structural capital for MI. Social implications ECFs that can be active in the international arena may maintain their services by financial sustainability. Thus, the advantage may result in a prosperous society. Originality/value The study is first to suggest a model joining IC and FR for the MI process of ECFs. This is suitable for competition of ECFs that are willing to be sustainable firms.