The purpose of this study was to explore the utility of chlorophyll fluorescence to non-destructively monitor water status in plant tissue, specifically water loss in grapes (Vitis spp.) destined for wine production. An automated remote-sensing (ARS), pulse amplitude modulation (PAM) fluorometer prototype, capable of scanning a large surface area, was used to monitor chlorophyll fluorescence from ‘L’Acadie’ (LAc) and ‘Thompson Seedless’-type (TS) grape clusters during postharvest dehydration. Increasing mass loss (%) in grapes correlated with increasing soluble solids (SS) content and decreasing osmotic potential (Ψ s ) (p<0.001). All of the primary fluorescence parameters monitored (F 0 , F m , F v and F v /F m ) had a strong curvilinear relationship (p<0.001) with grape mass loss. In both cultivars, F 0 increased during the later stages of dehydration, likely as a result of increased disorder within the thylakoid membranes and/or a reduction in energy transfer between LHCII and PSII. F m , F v and F v /F m declined, likely due to several factors that are known to inhibit photosynthesis and the primary charge recombination during osmotic stress. Chlorophyll degradation during dehydration was a major factor influencing cultivar differences in the fluorescence relationships. An inflection point in the F 0 value at ≈20–25% mass loss appeared to correspond with an inflection point in the decreasing glucose:fructose ratio. The relationship between chlorophyll fluorescence and water loss, SS, Ψ s and potentially other indicators of metabolic change, could lead to practical applications of this technology in the slow dehydration of grapes and other fruits used to make high value wines.