If you are a citizen of the Portuguese Republic or another European Union country, you can enter the Republic of Serbia without a visa, with a valid passport or ID card.
If in your national passport, you have a residence permit in the Portuguese Republic or another member of the European Union, the Schengen zone, or in the USA, as well as if you have a valid visa for the Schengen zone, a visa of a member of the EU, the UK or the USA, you do not need a visa to enter Serbia.
If you are in one of the mentioned categories, you can enter, transit, and stay in the Republic of Serbia for a maximum of 90 days in a period of six months, provided that the length of stay is in line with the validity period of the mentioned visas or residence permits.
You can find more information on the link Visa requirements.
If you are not a citizen of the Portuguese Republic and do not meet any of the above conditions for visa-free entry to the Republic of Serbia, you can check whether you need a visa with your national passport at the link Visa regime.
You can apply for a visa through the portal for foreigners, where you can find more information about the types of visas: "Welcome to Serbia".
You can find general information about entering the Republic of Serbia at the following link: General conditions for entering Serbia.