Compositions comprising cellulase and at least one poly alpha-1,3-glucan ether compound having a degree of substitution with an organic group of about 0.05-3.0 are disclosed. Such compositions can be dry or aqueous, the latter of which can have a viscosity of at least about 10 cPs. The disclosed composition can be in the form of a personal care product, household product, or industrial product, for example. Also disclosed are a method for preparing an aqueous composition comprising cellulase and a poly alpha-1,3-glucan ether compound, and a method of treating a material such as fabric by contacting it with this aqueous composition.