Shield: From the Provincial Seal of Samar where the town is located.
Sun w/ Fourteen Rays: Hope for future progress and development of town's fourteen (14) Barangays.
Red, White, & Blue Colors: From colors of Philippine National Flag; to show loyalty and patriotism of townspeople.
Cross-Sword: Christianity of townspeople and their aspiration for justice and equality.
Core Circle Divided Into Four: Poblacion, core of Municipality which is composed of four (4) Barangays.
Sea & Shrimp: Fishing as one of the main sources of income of Municipality; shrimp being dominant and bountiful marine resource in which San Sebastian is known for.
Mountain & Ricefield: Agriculture as other source of income of town; mountain represents upland farming, hilly portion of Municipality and rice land depict lowland farming with rice as its main crop.
Birds: Bio-life present in mountains.
1950: Year when Municipality was founded by virtue of Presidential Proclamation No. 208.