Mohr's research interests include cosmology, galaxy clusters, weak gravitational lensing, large scale structure and aspects of galaxy evolution. His research lies at the interface of theory and observations, where he employs multi-wavelength survey datasets and simulations to address key questions such as the underlying cause of the cosmic acceleration, the nature of dark matter and the behavior of gravity on the largest cosmic scales. In addition, he invests significantly in the planning and preparation for astronomical missions, developing scientific analysis and data handling software for the South Pole Telescope, the Dark Energy Survey, eROSITA, Euclid, MeerKAT and Rubin.