This chapter presents an overview of the relations between blend phase morphology and crystallization behavior and resulting semicrystalline structure in polymer blends with a crystallizable dispersed phase. Strong changes in the crystallization behavior, however, do occur as soon as the crystallizable polymer no longer forms a continuous phase but is forming discrete droplets within another polymer matrix, which is either crystalline or amorphous. A cocontinuous blend morphology consists of long, interpenetrating phase structures that lead to a network structure and is usually observed at relatively comparable concentrations of both blend components. During the meltmixing process, heterogeneous impurities can migrate across the interface between both blend phases, with the driving force being the interfacial free energy of the impurity with respect to its melt phase. For polymer blends, a strong correlation between the blend morphology and the crystallization behavior of the confined, dispersed phase is found.