Abstract : Red Pidada leaves (Sonneratia alba (L) Engl) have sun-protecting properties. Meanwhile, nanotechnology is widely used to extracted serum formula which are stable, safe, effective, and comfortable nanoparticle-sized. Therefore, this study targeted to formulate serum nanoparticles based on extracted Red Pidada leaves into a sunscreen serum preparation. It is detailed, nano serum was built in six formulas completed by different HPMC gelling agent concentrations, and evaluated stability in relation to the particle size, organoleptic, pH, viscosity, homogeneity, spraying pattern, irritation, and preference test. It showed the phytochemical screening carried out the extract contains alkaloids, flavonoids, saponins, tannins, and steroids. The detail finding explained the particle size was 308 nm, the color of the preparation was transparent white supported by distinctive smell. The completion of result study showed, the formulas had a semisolid gel dosage form, homogeneous, stable pH around 7.6-5.7, viscosity ranging from 401- 751 cps, and all fulfilled the physicochemical stability test criteria.