The exterior of the post office is made of metal and has many visible screws shown around it. It is tan in color, and has blue-colored circular windows along with a blue door which leads to the inside of the building. It has an arrow at the side of the building, pointing to the roof which contains many shapes to represent envelopes. It lastly has the words "Bikini Bottom Post Office" written on it in blue and red lettering, and the entire building is shaped like a box.
In the episode "Dear Vikings," SpongeBob writes a letter to the Vikings, but a Mailfish grabs it and leaves it in a bin. Soon after, a Viking, that works as a garbage man in Bikini Bottom, finds the letter and brings it to the King of all Vikings.
The post office is shaped like a cardboard box with all of the letters overflowing.
It is unknown if the Stamp Store is inside or connected in some way to the Bikini Bottom Post Office.