International travel outside of the United States is as easy for a legal permanent resident as it is for a U.S. citizen, as long as the travel period is less than one year. Green card holders are required to show their green cards upon departing and entering the country, as well as any reentry permits that apply. Green cards also act as visas for both Canada and Mexico, allowing entry to foreign citizens who would normally be required to obtain a visitor visa.
Keep your passport and green card with you at all times, both when departing the U.S. and reentering. Legal Permanent Residents, known as LPRs or green card holders, can travel in and out of the U.S. granted they have a valid passport. You must present your valid green card to the customs agent upon reentering the country; the green card acts as your visa. If your card is expired, you will be denied entry.
Apply for a reentry permit if you plan on traveling outside of the U.S. for more than one year. You must apply for a reentry permit through the United States Citizenship and Immigration Services, or you will be found in abandonment of your residence and your green card will be voided. Download Form I-131, Application for Travel Document, from the USCIS website and submit it along with the $360 application fee to the USCIS before you leave the country. (The application fee amount is current as of 2010.)
Apply for an application to preserve residency status if you are intending to apply for U.S. citizenship. If you plan to be outside of the U.S. for one year or more and you desire to maintain your three- or five-year continual residency status for naturalization purposes, you must file N-470, Application to Preserve Residence for Naturalization Purposes, simultaneously with I-131. N-470 can only be filed by those with a valid reason for an extended absence, such as a temporary foreign post with your private or government job or an assignment through a religious organization. Download N-470 from the USCIS website and submit it along with the $330 application fee simultaneously with I-131 and application fee to the USCIS before you leave the country.
Travel to Canada and Mexico without having to obtain a visa. U.S. green card holders of nationalities that are required to obtain visitor visas before entering Canada or Mexico are exempt from visa restrictions as long as they present their valid U.S. green card. For example, a Brazilian LPR in the United States does not need to apply for a visa to enter Canada as a tourist, even though Brazilians are normally required to obtain one before entering.