US green card holders can sponsor their parents for an immigrant visa, but they must first become US citizens through naturalization The process involves filing Form N-400, attending an interview, and taking the Oath of Allegiance Once a citizen, they can file Form I-130 to establish the parent-child relationship and prove financial support with Form I-864. Parents can go through consular processing or adjust their status if in the US before attending visa interviews Upon approval, they receive immigrant visas or green cards Challenges include lengthy processing times, documentation issues, interviews, and background checks Health and security clearances are also required Keeping up with immigration law changes is vital By following the steps and preparing for challenges, green card holders can successfully sponsor their parents for an immigrant visa after naturalizing