The pharmaceutical market has entered an era in which the production of new therapeutics is being often replaced by "biosimilars", copies of already commercialized products waiting for the patents to expire in order to be distributed in a more competitive and affordable manners. Due to its relevance, the ErbB2-targeted monoclonal antibody Trastuzumab (Herceptin) used as breast cancer therapy is one of the main targets in the production of biosimilars. A major challenge is to produce antibodies with the same or the closest N-glycosylation pattern seen in the commercialized drug. Several factors, such as growing conditions or cell types employed, can determine the final composition and structure of the glycans, significantly affecting the properties of the generated antibodies. Therefore, an appropriate characterization is essential. In the present study, we describe two different but complementary strategies to characterize the N-glycosylation of two biosimilar candidates of Trastuzumab. In the first case, N-glycans are fluorescently labeled and separated by Normal Phase HPLC. Different sugars will elute at different times and can be identified using specific oligosaccharide standards. In the second approach, released glycans are permethylated and analyzed by MALDI-TOF MS, being able to determine the structure because of the differential sugar masses. The characterization of the N-glycosylation sites of therapeutic recombinant monoclonal antibodies (mAbs) is usually one of the most critical and time consuming steps in the developing process of biosimilars or any other glycosylated drug. Herein we describe two different but complementary approaches to characterize mAbs glycosylation patterns, the use of glycan fluorescence labeling coupled to HPLC and MALDI-TOF MS profile analysis. This article is part of a Special Issue entitled: HUPO 2014.