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Histone chaperones mediate assembly and disassembly of nucleosomes and participate in essentially all DNA-dependent cellular processes. InArabidopsis thaliana,loss-of-functions of FAS1 or FAS2 subunits of the H3-H4 histone chaperone complex CHROMATIN ASSEMBLY FACTOR 1(CAF-1) has a dramatic effect on plant morphology, growth and overall fitness. Altered chromatin compaction, systematic loss of repetitive elements or increased DNA damage clearly demonstrate the severity of CAF-1 dysfunction. How histone chaperone molecular networks change without a functional CAF-1 remains elusive. Here we present an intriguing observation that disruption of the H2A-H2B histone chaperone NUCLEOSOME ASSEMBLY PROTEIN 1 (NAP1) supressesFAS1loss-of function. The quadruple mutantfas1nap1;1-3shows wild-type growth and decreased sensitivity to genotoxic stress. Chromatin offas1nap1;1-3plants is less accessible to micrococcal nuclease and progressive loss of telomeres and 45S rDNA is supressed. Interestingly, the strong genetic interaction betweenFAS1andNAP1does not occur via direct protein-protein interaction. We propose that NAP1;1-3 play an essential role in nucleosome assembly infas1,thus their disruption abolishesfas1defects. Our data altogether reveal a novel function of NAP1 proteins, unmasked by CAF-1 dysfunction. It emphasizes the importance of a balanced composition of chromatin and shed light on the histone chaperone molecular network.