  We propose a new method to test modified gravity theories, taking advantage
of the available data on extrasolar planets. We computed the deviations from
the Kepler third law and use that to constrain gravity theories beyond General
Relativity. We investigate gravity models which incorporate three screening
mechanisms: the Chameleon, the Symmetron and the Vainshtein. We find that data
from exoplanets orbits are very sensitive to the screening mechanisms putting
strong constraints in the parameter space for the Chameleon models and the
Symmetron, complementary and competitive to other methods, like interferometers
and solar system. With the constraints on Vainshtein we are able to work beyond
the hypothesis that the crossover scale is of the same order of magnitude than
the Hubble radius $r_c \sim H_0^{-1}$, which makes the screening work
automatically, testing how strong this hypothesis is and the viability of other
scales.
