Engineer (of contract) is a special institution of building law, though not normalized at present by Polish legislator. Based only on the internationally harmonized FIDIC conditions of contract, as an institution of foreign origin its use is conditional upon the occurrence of the construction projects financed by foreign entities. The article aims to demonstrate the relationship existing between the participants in the construction process, directly specified in the Act – Construction Law. The engineer carries out his or her duties by contract with the investor, which determines their joint responsibilities and powers, with particular emphasis on those that the legislature imposes on the investor’s supervision inspector. They put forward the thesis that the contract engineer is a sui genris participant in the construction process, as his or her duties and powers are closely related to those of the persons who exercise independent technical functions in the construction industry (in particular the obligations of the investor’s inspector). The article introduces the institution of the engineer, subject only to a few studies of industry practices in the construction process, especially if it is based on funding agreements with foreign entities, in particular in connection with the EU programs.