Lignocellulosic biomass is an abundant and renewable source that could be utilized for production of many bioproducts. It mainly consists of cellulose, hemicellulose, and lignin, all of which come together to form a recalcitrant wall that impedes production of bioproducts. In order to overcome the recalcitrant nature of the biomass, it is important to fully understand how cell wall components are synthesized and assembled. Xylan is one of the hemicellulosic components of the wall that contributes to recalcitrance. Xylan has substitutions on the backbone that are formed by the orchestration of many enzymes. For example, glucuronoxylan methyltransferases are responsible for 4-O-methylation of glucuronic acid (GlcA) side chains on xylan. Mutant lines are valuable sources to understand the structure and importance of xylan. Here, we investigated the wild-type and gxm1gxm2gxm3 triple mutant of Arabidopsis by employing a set of four xylan antibodies that specifically recognize methyl glucuronoxylan epitopes on xylan to prove their epitope. The triple mutant cell walls were observed with methyl glucuronoxylan specific monoclonal antibodies for the first time. Cell-wall-directed antibodies could help further our understanding on the synthesis and structure of plant cell walls.