The assessment of photosynthetic pigments is a reliable indicator for evaluating plant productivity and environmental stress. Therefore, developing an in-situ method for monitoring photosynthetic pigments is essential for effective tea crop management. Hyperspectral reflectance has been widely applied to assess vegetation properties, including pigment content, using portable spectroradiometers. However, the cost of these devices remains high and inaccessible for general use. This study evaluated the potential of an unmanned aerial vehicle (UAV)-mounted hyperspectral sensor incorporating a cost-effective, fingertip-sized spectrometer (C12880MA-10, Hamamatsu Photonics K.K.) to estimate chlorophyll and carotenoid content in tea leaves using the PROSPECT-D+SAIL model. Based on the ratio of performance to deviation (RPD), the proposed approach demonstrated effective performance in estimating both chlorophyll and carotenoid content, with RPD values exceeding 1.4.