How to Apply for US Citizenship With a Green Card: N-400 Step-by-Step Guide

For millions of lawful permanent residents in the United States, the day they become eligible to apply for U.S. citizenship feels like the finish line of a long, difficult journey. If you are a green card holder wondering how to apply for U.S. citizenship, you are in the right place. This guide walks you through the entire N-400 naturalization process — from checking your eligibility to attending your oath ceremony.

Understanding each step before you begin makes the process far less stressful — and helps you avoid costly mistakes that can delay or jeopardize your application.

Who Can Apply for US Citizenship With a Green Card?

To apply for U.S. citizenship through naturalization, you generally need to meet the following requirements as a green card holder:

Continuous residence: Most green card holders must have been a lawful permanent resident for at least 5 years before applying. If you are married to a U.S. citizen and have lived with your spouse, this is reduced to 3 years.

Physical presence: You must have been physically present in the United States for at least 30 months out of the 5 years before filing (or 18 months out of 3 years if married to a U.S. citizen). Trips abroad longer than 6 months can interrupt your continuous residence and affect your eligibility.

Good moral character: USCIS requires that you have demonstrated "good moral character" during the required residence period. Certain criminal convictions can disqualify you or require additional review.

English language: You must be able to read, write, and speak basic English. There are exceptions for older applicants who have held a green card for a long time.

Civics knowledge: You must be able to pass a civics test covering U.S. history and government. USCIS provides a list of 100 possible questions; you will be asked up to 10 and must answer 6 correctly.

Step 1: Confirm Your Eligibility and Review Your Record

Before you file anything, review your immigration and criminal history carefully. Check that your continuous residence period is intact and that there are no gaps or issues in your record that could affect your application. If you have any arrests or any periods outside the U.S. longer than 6 months, consult with an immigration attorney before filing.

Step 2: Complete Form N-400

Form N-400, Application for Naturalization, is the official USCIS form used to apply for U.S. citizenship. It asks for detailed information about your background, residence history, employment, travel abroad, and more. Take your time completing the N-400 carefully and accurately. Any inconsistencies between your N-400 and your immigration records can trigger questions at your naturalization interview.

Step 3: Gather Supporting Documents

Along with your completed N-400, you will need to submit a copy of your green card (front and back), two passport-style photos, the USCIS filing fee (currently $725 for most applicants — check the USCIS website for the most current amount as fees are subject to change), and any additional documents required based on your specific situation.

Step 4: Submit Your Application

Mail your completed N-400 and supporting documents to the USCIS lockbox facility that serves your area. After USCIS receives your application, you will receive a receipt notice with a unique case number you can use to track your case online.

Step 5: Attend Your Biometrics Appointment

USCIS will schedule you for a biometrics appointment at a local Application Support Center. At this appointment, they will collect your fingerprints and photograph for a background check. Bring your appointment notice and a valid photo ID.

Step 6: Prepare for and Attend Your Naturalization Interview

At your naturalization interview, a USCIS officer will review your N-400, ask you questions about your application and background, test your English, and administer the civics test. To prepare, study the 100 official civics questions on the USCIS website, practice answering questions about your application clearly and honestly, and bring all original documents that correspond to copies you submitted with your N-400. Most interviews take 20 to 30 minutes.

Step 7: Receive a Decision

After your interview, USCIS will inform you of one of three outcomes: approval, continuation (meaning more information is needed), or denial. If your application is approved, you will be scheduled for an oath ceremony.

Step 8: Take the Oath of Allegiance

The final step in becoming a U.S. citizen is attending an oath ceremony and taking the Oath of Allegiance to the United States. At this ceremony, your green card will be collected, and you will receive a Certificate of Naturalization — your official proof of U.S. citizenship.

Common Mistakes to Avoid When Applying for US Citizenship With a Green Card

Filing too early is a common error. If you file before you have met the continuous residence and physical presence requirements, your application will be denied. Incomplete or inconsistent answers on the N-400 also create red flags — every question matters. Not disclosing arrests is another serious mistake; even arrests that did not result in a conviction must generally be disclosed. Long trips abroad can interrupt your continuous residence, so if you have taken any trips longer than 6 months, speak with an attorney before filing.

How Fibi Law Can Help

Applying for U.S. citizenship with your green card is a major milestone — and one you want to get right. At Fibi Law, our citizenship and naturalization attorneys guide green card holders through every stage of the N-400 process, from reviewing your eligibility and preparing your application to coaching you for your naturalization interview.

We serve clients across Philadelphia, New Jersey, New York, Atlanta, and the Bronx, and we understand the unique circumstances that different communities face on the path to citizenship. Our team can help you evaluate your eligibility, identify any potential issues before you file, and make sure your application gives you the best possible chance of approval.

Ready to take the next step toward U.S. citizenship? Contact Fibi Law today for a consultation. U.S. citizenship is within reach — and our team is here to help you get there.