The level scheme of 153Ho has been studied to a spin of and Ex=12.5 MeV using γ-ray and conversion-electron spectroscopy techniques. Two isomeric levels, with are observed. Above 2.7 MeV the yrast line displays the irregular level spacing characteristic of single particle alignment. Shell-model configurations are suggested for most states below 9.1 MeV, in which the 3− octupole vibration may play a major role.