A new and improved case sealer assembly comprises a pair of oppositely disposed case drive mechanisms for conveying a multiplicity of cases through a sealing station. The drive mechanisms are laterally separated from each other such that an interior space is formed therebetween which effectively defines a sealing station for serially accommodating the multiplicity of cases to be sealed. The pair of drive mechanisms are mounted upon arms that are movably mounted in a linear manner so as to be capable of being manually adjusted toward and away from each other in a substantially infinite number of increments, and in addition, the arms are also pivotally mounted such that not only are the drive mechanisms manually movable toward or away from each other in order to initially adjust the lateral distance, defined between the pair of oppositely disposed drive mechanisms, to any one of an infinite number of predetermined dimensions whereby various different cartons or cases, having various, different predetermined width dimensions, can be accommodated by the case sealer assembly, but in addition, the pair of oppositely disposed drive mechanisms are mounted for automatic expansible movement with respect to each other so as to accommodate various different cases having various different width dimensions within a predetermined range of width dimensions.