Chemical modification of cellulose nanocrystals (CNC) is an interesting alternative to prepare chemical cross-linked nanocellulose-based gels. In this work, chemically cross-linked CNC gels were prepared by the reaction of aldehyde-functionalized CNC and two different diamines: ethylenediamine (ED) and 4,4′-(1,3-phenylene dioxy)dianiline (PDD). Chemical modifications were verified by FTIR and POM. The formation of a solid gel was achieved when PDD was used as the cross-linking agent.