This paper aims to demonstrate the effect of polypropylene and wool fibers on the mechanical properties of concrete, particularly in view of the increasingly important environmental issues and the use of sustainable resources. Due to the fact that there is a significant quantity of wool on the islands of Cres and Krk that is not used for other purposes, an idea emerged to use it in concrete instead of polypropylene fibers. The paper's focus is to determine whether the use of wool fibers as a component of micro – reinforced concrete is justified. In that regard, experimental tests for compressive strength, flexural strength, and modulus of elasticity were conducted. All tests are in accordance with current European standards and the corresponding Croatian national annexes. The paper provides a review of the existing research on the impact of polypropylene fibers on the mechanical properties of concrete. The subject of concrete reinforced with wool fibers is currently scantily explored in the scientific community, hence the paper presents a single study that addressed a similar subject. The tests were performed on samples with 0.50%, 1.00%, 1.50%, and 2.00% polypropylene fibers and 0.50% wool fibers. An identical recipe and curing process were used for all mixtures to ensure that the type and quantity of fibers could be accurately associated with the results. Furthermore, the paper determined that polypropylene and wool fibers result in an increase in compressive and flexural strength compared to reference concrete. Ultimately, it is concluded that the modulus of elasticity of the sample containing wool fibers is higher compared to concrete with added polypropylene fibers.