Fibers have been widely applied to improve the mechanical properties of natural soil and traditional cemented soils, but rarely investigated in substrates for slope eco-protection. Vegetation-growing concrete (VC) substrate is a kind of ecological cemented soil and has very wide popularization and application prospects. In this study, unconsolidated-undrained (UU) triaxial compression tests were conducted on the control specimens of VC substrate containing three cement contents and the palm fiber reinforced specimens manufactured by adding four fiber contents. The control specimens were shown to possess increasing yield strength, ultimate strength, yield strain and shear modulus with cement content, which resulted from the cemented texture improved by the hydrate products as recognized previously. Instead of inextensible reinforcement provided by cement, the palm fibers were found to provide extensible reinforcement, through which the obvious softening behavior of VC substrate could transfer to elasto-plasticity. Attributed to the unique ductility, the fibers added could bring with considerable increase in ductility of reinforced substrate, except for additional increases in yield strength, ultimate strength and yield strain.