Biostimulants are natural products for organic farming that help improve production and final food quality, reduce plants’ vulnerability to environmental stresses, and limit inorganic product use. Sustainable management enhancement of agricultural systems has led to the introduction of precision farming technologies based on remote sensing data acquisition, crucial for input optimization and derived effects monitoring. The work aims to monitor and evaluate four biostimulant rates application effect on grapevines’ water status through UAS-derived vegetation indexes, comparing the results with those acquired from a Scholander pressure chamber for Stem Water Potential (SWP) evaluation. NDVI and NDRE vegetation indexes and SWP were analysed at parcel levels following a randomized complete block design in a Malvasia Bianca cultivar vineyard located in Sardinia (Italy) during 2020 and 2021 seasons. The results showed that the vegetation indices, in agreement with conventional ground measurements, made it possible to assess vegetative growth temporal evolution, revealing no differences between the fertilization strategies, evident only in grapes’ production results. The causes probably stem from the insufficient biostimulant rate applications, unable to provoke a different response on the cultivar detectable from vegetation indexes and SWP. Further studies will evaluate the ability of remote and proximal sensing technologies to validate precision viticulture operations benefits, especially on a long-term survey.