  The small-cluster exact-diagonalization calculations and the projector
quantum Monte Carlo method are used to examine the competing effects of
geometrical frustration and interaction on ferromagnetism in the Hubbard model
on the Shastry-Sutherland lattice. It is shown that the geometrical frustration
stabilizes the ferromagnetic state at high electron concentrations ($n \gtrsim
7/4$), where strong correlations between ferromagnetism and the shape of the
noninteracting density of states are observed. In particular, it is found that
ferromagnetism is stabilized only for these values of frustration parameters,
which lead to the single peaked noninterating density of states at the band
edge. Once, two or more peaks appear in the noninteracting density of states at
the band egde the ferromagnetic state is suppressed. This opens a new route
towards the understanding of ferromagnetism in strongly correlated systems.
