We consider the potential detection of chameleons using bouncing ultracold neutrons. We show that the presence of a chameleon field over a planar plate would alter the energy levels of ultra cold neutrons in the terrestrial gravitational field. When chameleons are strongly coupled to nuclear matter, β≳ 10^8, we find that the shift in energy levels would be detectable with the forthcoming GRANIT experiment, where a sensitivity of order one percent of a peV is expected. We also find that an

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... ely large coupling β≳ 10^11 would lead to new bound states at a distance of order 2 microns, which is already ruled out by previous Grenoble experiments. The resulting bound, β≲ 10^11, is already three orders of magnitude better than the upper bound, β≲ 10^14, from precision tests of atomic spectra.