Traditionally, the rheological properties of magnetorheological (MR) fluids are investigated under uniaxial steady (DC) fields. These basic fields promote the aggregation of magnetically attractive particles into chain-like structures aligned in the field driven direction. In this manuscript we show how triaxial unsteady fields can generate a variety of exotic mesostructures and influence the rheological response of the MR fluids. We bridge understanding the rheological response to each unique particle structure through videomicroscopy, x-ray microtomography and rheometry tests. Small-amplitude oscillatory shear and steady shear tests lay out an unmistakable argument for MR enhancement with both elevated storage modulus and yield stress responses following a sequence of steady uniaxial and unsteady fields. We demonstrate that structures assembled through time-averaged particle interactions or typical dipole–dipole magnetostatic interactions, especially when columnar structures are strengthened through lateral chain coalescence, can boost rheological response.