The façade out-of-plane failure is one of the most typical local mechanism in masonry churches recognizable in the aftermath of a seismic event. The analysis of such a failure is addressed in this paper with reference to a case study of twenty ancient churches hit by the seismic event of 21^st August 2017 in the Ischia Island (Italy). The main aim is the definition of the capacity curves of the façades and their seismic assessment based on the seismic input. The non-linear static analysis of the rocking masonry façade is developed according to the displacement-based approach. The pushover analysis is carried out considering geometric nonlinearity, namely by evaluating the static multiplier for varied kinematic configurations while a macro-block model is adopted involving the stabilising contribution of frictional resistances exerted by the side-walls. The effect of the interlocking between the façade and the sidewalls of the churches gradually decreases due to the non-linear variation of the frictional resistances. On the other hand, the seismic demand is represented by ADRS (acceleration-displacement response spectra) curves provided by both selected real accelerograms and the Italian seismic code. The capacity is compared with the seismic demand through safety indexes for different limit states, in terms of both forces and displacements, and the relevant influence of the frictional resistances on increasing the capacity is discussed. Finally, the obtained capacity curves are critically discussed to identify homogeneous classes for the analysed façades in terms of vulnerability, in order to implement future statistical analyses and fragility curves.