Novel ultrafiltration membranes are prepared from solution of cellulose in ionic liquids by phase inversion on filter paper as support. Membrane performance can be adjusted by varying the casting solution composition. The addition of dimethyl sulfoxide leads to a change in solvent quality of the used ionic liquid, which has a direct influence on the membrane structure formation. However, it does not have a big influence on the membrane performance but can benefit the processing of cellulose to membranes via reducing the viscosity of the solution and costs by decreasing the amount of ionic liquid.