In this paper, the concept of cosine-modulated multifilter (CMMF) and the formulation of a class of cosine-modulated multifilters are proposed in order to take advantages of both cosine-modulated filter banks and multifilters. Specifically, the low-complexity in implementation of cosine-modulated filter bank can provide a way to overcome the high-complexity in design of the multifilters. Constrains on the prototype filter for the resulting CMMF to be paraunitary are stated and the design method is presented. Besides providing all the advantages that multifilters have, the proposed method has two major advantages over the existing multifilter design methods. First, all the filters in an M-band N-channel multifilter are cosine-modulated version of a single prototype filter, hence design complexity is significantly reduced. Second, the implementation is greatly simplified and efficient, especially when fast algorithm, such as fast DCT and FFT, are used in the cosine modulation case and exponential modulation case. Design examples are also presented.