Carbohydrates perform important physiological functions in eukaryotic and prokaryotic cells. Indeed, alterations in glycan patterns may be associated with disorders. The analysis of these sugars can be reached using nanoprobes composed by lectins associated with fluorescent nanoparticles. This study reports the conjugation of a galactose-binding lectin (BmoLL) isolated from Bauhinia monandra leaves with quantum dots (QDs) by adsorption. QDs-BmoLL conjugates showed bright fluorescence and the hemagglutination assay revealed that the lectin preserved its carbohydrate-binding ability after the conjugation. To evaluate the efficiency/specificity of the bioconjugate, ABO human red blood cells (RBCs) were used as biological models and the labeling was analyzed by flow cytometry. Among ABO blood groups, higher labeling (71.7 ± 5.9%) was detected for B-type RBCs, whose antigens have galactose in their structure. The specificity of labeling was confirmed since A- and O-types RBCs incubated with QDs-BmoLL, as well as B-type cells incubated with previously galactose-inhibited conjugates, were labeled below 6%. In AB-type RBCs, which simultaneously have B and A (N-acetylgalactosamine) antigens on their membrane, the labeling was ca. 14.1 ± 4.8%. Therefore, a successful conjugation was reached and QDs-BmoLL conjugates can be considered promising fluorescent nanoprobes for biological investigations.