The layered Ruddlesden−Popper derivatives of CH 3 NH 3 PbI 3 have recently emerged as high-performing materials for photovoltaics with improved stability. The inclusion of organic molecules within the inorganic framework provides additional dynamic degrees of freedom that influence the optoelectronic properties. The rotational dynamics of CH 3 NH 3 + influence dielectric behavior and electronic excited-state dynamics in CH 3 NH 3 PbI 3 ; however, the influence of cation dynamics on properties in the layered derivatives has not yet been determined. We employ quasi-elastic neutron scattering to study the rotational dynamics of methylammonium (CH 3 NH 3 + , MA) and deuterated nb u t y l a m m o n i u m ( + CD (CD ) NH 3 2 3 3 , d -n B A ) i n ( d -nBA) 2 (MA) n−1 Pb n I 3n+1 (n = 2, 3). (d-nBA) 2 (MA) 2 Pb 3 I 10 exhibits shorter residence times of the CH 3 NH 3 + and + CD (CD ) NH 3 2 3 3 reorientational motions, which are attributed to the larger volumes that the cations occupy in the inorganic framework and to the dimensionality of the inorganic layer by way of dielectric screening between the organic cations. Discontinuities in the mean-squared displacement of overall hydrogen motion determined by fixedwindow elastic neutron scattering are consistent with phase transitions observed by differential scanning calorimetry and timeresolved microwave conductivity signals. Determining how the dimensionality of the inorganic layer influences the organic cation rotational dynamics provides fundamental chemical insight into how the electronic dynamics vary between n-members.