The cross section for the Sm149(n, α)Nd146 reaction at thermal neutron energies was measured by observing the alpha-particle spectrum of natural Sm and isotopically enriched Sm149 targets in the thermal column of a reactor. Alpha-particle groups were observed at 8.72 and 9.12 MeV corresponding to transitions to the first excited state and ground state of Nd146. The 2200-m/sec cross sections (σ0) for the two groups were calculated to be 121+/-15 mb and 22+/-10 mb, respectively, from the experimental results. The 4- resonance at 0.0967 eV accounts for most of the cross section to the first excited state, but cannot contribute to the population of the ground state. It is postulated that the population of the ground state arises from a contribution of a bound 3- state in Sm150. Calculated values for the (n, α) cross section are compared with the experimental results.