An agronomic research was conducted to evaluate the spatial variability of an onion crop, with the aim to test Vegetation indices (VIs) as a tool to detect different yield areas. Eleven VIs were derived from geo-referred hyperspectral readings taken at bulbification stage. Eight VIs showed significant regressions with yield, and grouped in four clusters according to statistical analysis (H = high; Ms and Mi as medium superior and inferior; L = low). Maps were elaborated with ordinary Kriging. At a visual assessment, many VIs appeared similar to yield map. The surface analysis revealed that all VIs accurately detected an L area (top of maps) characterized by heavy soil constrains, and the H area on the left side of the map (button and upper part). The best estimation of the total field yield was obtained by the so-called Soil-line vegetation indices and in particular by TSAVI. This study reinforces the possibility of assessing onion yield by spectroradiometric measurements at field scale.