Mechanisms of the cryoprecipitation of cryoglobulins have long been studied but not fully understood. In the present study, we characterize a monoclonal immunoglobulin G1 (IgG1) cryoglobulin that forms sharp needle crystals upon cooling and therefore might be an ideal example for the elucidation of a mechanism of cryoprecipitation of cryoglobulins. Limited proteolysis by papain of this cryoglobulin resulted in disappearance of cryocrystallization. Interactions of the proteolytic fragments were examined by surface plasmon resonance measurements. A temperature-dependent isologous Fab-Fab interaction was observed for this cryoglobulin. Glycosylation profiling by use of the HPLC mapping technique revealed that cryoglobulin expresses homogeneous N-glycans in its Fc portion. These results suggest that (1) the temperature-dependent crystallization of the cryoglobulin was ascribed to its specific Fab-Fab interaction and (2) the unusual homogeneity of the Fc glycosylation promote the crystallization of this cryoglobulin.