Conventional finite element updating techniques make use of measured frequency response functions and modal parameter estimates to update the FE model parameters. This paper presents a new technique to update the FE model from output-only transmissibility measurements assuming the location of the excitation force is known. A transmissibility function is defined as the ratio between two (measured) responses. In general, the poles that are identified from transmissibility measurements do not correspond with the system's poles. It can be proven that the peaks of the transmissibility function coincide with the modal frequencies of the system with the excitation degree of freedom constrained. The effectiveness of the proposed procedure will be illustrated by means of a case study.