We show the possibility to discover the neutrino nature by measuring the Majorana CP phase at the DUNE experiment. This phase is turned on by a decoherence environment, possibly originated by physics at the Planck scale. A sizable distortion in the measurement of the Dirac CP violation phase δCP is observed at DUNE when compared with T2HK measurement due to decoherence and the non-null Majorana phase. Being that, when the measurement of the Majorana phase is performed at DUNE, it reaches a precision of 23(21)% for a decoherence parameter Γ=4.5(5.5)×10-24 GeV and a Majorana phase equal to 1.5π. The latter precision is similar to the one obtained at the T2K experiment at its current Dirac CP violation phase measurement.