The neutron-rich praseodymium isotopes 151Pr and 153Pr have been studied by prompt γ-ray spectroscopy using 248Cm and 252Cf spontaneous-fission sources placed inside the EUROGAM-II and Gammasphere germanium arrays, respectively. Rotational bands based on 3/2 -[541] states, with similar structures, have been assigned to these nuclei. These bands decay by intraband E2 transitions. Interband E1 transitions, reported in other works, were not observed. Delayed conversion-electron and γ-ray spectroscopy of an A=151 nucleus has been performed at the Lohengrin mass spectrometer. A previously reported 35.1-keV isomer of 151Pr has been determined to decay by an E1 transition, and its half-life of 50(8) μs has been measured. Calculations performed using a reflection-symmetric quasi-particle-rotor model successfully reproduce the energies of the excited states of these nuclei and their decay patterns. The spin of the isomer has been assigned to be (1/2 +, 3/2 +) from a comparison with the calculations. The long half-life of this isomer and the lack of intraband E1 transitions show an absence of strong octupole correlations in the observed states of 151 ,153Pr. This is explained in terms of increasing quadrupole deformation reducing the number of Nilsson orbitals close to the Fermi surface available to form octupole collectivity. ©2012 American Physical Society.