Updated project metadata. For the unicellular alga Chlamydomonas reinhardtii, the presence of N-glycosylated proteins on the surface of two flagella is crucial for both cell-cell interaction during mating and flagellar surface adhesion. However, it is not known whether only the presence or also the composition of N-glycans attached to respective proteins is important for these processes. To this end, we tested several C. reinhardtii insertional mutants and a CRIPSR/Cas9 knockout mutant of xylosyltransferase 1A, all possessing altered N-glycan compositions. Taking advantage of atomic force microscopy and micropipette force measurements, our data revealed that reduction in N-glycan complexity impedes the adhesion force required for binding the flagella to surfaces as demonstrated by force spectroscopy and impairs polystyrene bead binding and transport. Notably, assembly, Intraflagellar Transport and FMG-1B transport into flagella are not affected by altered N-glycosylation. Thus, we conclude that proper N-glycosylation of flagellar proteins is crucial for adhering C. reinhardtii cells onto surfaces, indicating that N-glycans mediate surface adhesion via direct surface contact. Data deposited here include IS-CID data verifying altered N-glycan patterns in flagella of mutants analysed (Ursgal-SugarPy-flagella-IM-results.xls) as well as the N-glycoproteomic characterization of the novel CRISPRXylT1A mutant (Ursgal-SugarPy-CIRSPR-mutant-results.xls). Regarding the latter, PRM measurements verifying the knock out of XylT1A are also deposited here (Results_PRM-measurement_quantification_GT.xls). Further, label free quantification data on isolated flagella of original IM strains verifying that altered N-glycosylation does not impact flagellar protein localization can be found within this dataset (Flagella_IM-WT_ normalized_5_proteins.pdResult).