The seal is enclosed by a circle which symbolizes the binding together of all the residents of the municipality.
Inscribed on the upper half of the narrow circular space formed by the outer and inner circles are the words “Municipality of San Mateo,” punctuated by a dot on the mid left and on the mid right and the half portion on the circular space are inscribed the words “Province of Isabela.”
Inside the smaller circle is the shield-like figure. This is derived from the provincial seal of Isabela where the town is located. The drawings of rice fields, irrigation system, palay and corn depict that farming is the main source of income and rice is the major crop and the vast rice field is fully irrigated. The background color is greenish indicating lush vegetation. Below the shield-like figure is the founding year, 1946.