The functional role of the complex pectic rhamnogalacturonane I (RGI) in the context of cell biology is still unclear. RGI is mainly composed of a repeating disaccharide unit [,2)-a-L-rhamnosep-(1,4)-a-D-galacturonic acidp-(1,]n (RU)n decorated primarily with arabinan and (arabino)-galactan side-chains. Monoclonal antibodies (mAbs) are useful to probe pectin structural domains in situ. Several mAbs to the RGI backbone and to arabinan and (arabino)-galactan side-chains have been developed but up to now, there is no mAb against rhamnogalacturonan stretches bearing arabinose or galactose units. Here, we report on the production and fine characterisation of new mAbs against RGI side chains connected to the rhamnogalacturonan backbone. The study first focused on the generation of adequate antigens. A pool of low-branched RU oligosaccharides was prepared and purified from potato pulp. mAbs were raised against low-branched RU oligosaccharides-ovalbumin conjugates. Promising clones producing mAbs recognizing low-branched RU oligosaccharides but recognizing neither unbranched RU oligosaccharides nor galactan oligosaccharides were recovered. The combination of glycan microarray and sub-fractionation of the low-branched RU oligosaccharides pool by anion exchange chromatography prior to competitive ELISA studies allowed fine mAbs characterisation. The use of these new mAbs in immunocytochemistry is expected to give a better understanding of RGI role in planta.