The use of thin cement based panels reinforced with relatively high content of Recycled Steel Fibres (RSF) for the shear strengthening of Reinforced Concrete (RC) beams is investigated in the present work. The mechanical properties of this Recycled Steel Fibre Reinforced Mortar (RSFRM) are characterised. The panels are produced by using a mixing technique similar to the one used in the slurry infiltrated fibre concrete technology. Then, their potentialities as a shear strengthening solution for RC beams deficiently reinforced in shear are investigated by performing three-point bending tests with RC beams of “I” shape cross section. The RSFRM panels are applied in the lateral faces of the beams by using the two following strategies: (1) bonded to the concrete substrate by applying exclusively epoxy adhesive; and (2) besides epoxy adhesive, mechanical fasteners are applied. The applicability of an analytical approach for estimating the contribution of RSFRM panels for the shear resistance of RC beams is assessed, and a design example is presented.