Recently,a 16-day periodicity in a fast radio burst was reported.We propose that this 16-day periodicity may be due to forced precession of the neutron star by a fallback disk.When the rotation axis is misaligned with respect to the normal direction of the disk plane,the neutron star will precess.The ec-centricity of the neutron star may be due to rotation or strong magnetic field,or similar reasons.We found that the 16-day period may be understood using typical masses of the fallback disk.Polarization observa-tions and information about the neutron star rotation period may help to discriminate different models.The possible precession observations in pulsars,magnetars and fast radio bursts may be understood together considering forced precession by a fallback disk.