If you are a U.S. citizen with foreign-born parents, you can apply for green cards (lawful permanent residence) for them provided you are at least 21 years old. Parents of U.S. citizens are considered to be "immediate relatives" under U.S. immigration laws. That's good, because it means there is no annual limit on the number of green cards given out in this category and therefore no waiting list (when demand exceeds supply) to slow down their application process. But you'll face many other requirements and hurdles, as we'll discuss below, focusing on:
It's important to realize that your foreign-born parents can be denied green cards if they are inadmissible to the United States on any of various grounds, such as:
Your parents will need to not only answer many questions about these topics, but undergo specialized medical exams and have any missing vaccinations done, possibly provide their fingerprints and obtain police certificates, and more.
One ground of inadmissibility that can be especially troublesome when petitioning for parents, particularly if the petitioner (you) are relatively young, is the "public charge" rule. You will need to show sufficient income or assets to support or sponsor your parents in an amount that's at least 125% of the U.S. Poverty Guidelines. This rule is intended to make sure your parents aren't inadmissible to the United States as likely "public charges," meaning people seen as likely to draw on need-based government assistance.
To see the current poverty guidelines levels, see Form I-864P. They tend to go up every year with inflation. Calculating the exact amount of income and assets you'll need to show will take be partly based on how many household members or dependents you are already supporting. By the way, this is an obligation that will last around 10 years, and your parents can sue you if you fail to support them.
To start the immigration process, you'll need to fill out Form I-130, also called Petition for Alien Relative; a form issued by U.S. Citizenship and Immigration Services (USCIS). The petition is meant to prove your status as a U.S. citizen and the child-parent relationship that exists between you and your parents, now known as your "beneficiaries."
You will need to include both a copy of your U.S. passport, naturalization certificate, or other proof of citizenship, as well as your birth certificate showing your parents' names, or similar proof of their relationship to you. (Don't send originals of these or any documents—you will likely never get them back.) If you are petitioning for both of your parents, you'll need to submit two separate I-130 petitions.
If one of your parents is a stepparent, you can petition for them as an immediate relative if the relationship was formed (that is, if the marriage to your biological or adoptive parent) took place before you turned 18 years old. In this situation, you'd also need to include a copy of their marriage certificate plus proof of how the previous marriage (if any) ended, such as a death certificate or divorce decree.
As soon as the I-130 petition has been approved by USCIS, assuming your parents live overseas, the agency will forward the file to a U.S. consulate in your parents' home country. The consulate will communicate with them about how they can submit their own required application forms and documents.
You'll need to submit an Affidavit of Support on USCIS Form I-864 during this stage of the process. Before long, the consulate will give your parents information on getting their medical exam done, then call your parents in for an interview. At that time, or soon after, their immigrant visa should be approved. (Security checks often introduce delays at this stage.) With that visa in hand, they can enter the United States and become lawful permanent residents.
If your parents happen to be in the United States after a legal entry, such as with a visa, then yes, as your immediate relatives it might be possible for them to apply for a green card without leaving the United States. This is a process called "adjustment of status." But don't read this and say, "Oh, I'll simply have my parents enter the United States as tourists and apply to adjust status." That's a fraudulent misuse of the tourist visa, and can lead to their green card applications being denied.
If they entered the United States without inspection (such as by having been smuggled across the border) they cannot adjust status (with rare exceptions)—and should talk to an immigration attorney about whether they can realistically immigrate at all, since living in the United States unlawfully for anything longer than six months creates a long-term bar to admissibility. (Although waivers are available to some people (using Form I-601A), these typically don't work for parents of U.S. citizens, because they'd need to have a spouse or parent who is a U.S. citizen or green card holder; having a U.S. citizen child doesn't count for this waiver.)
If your parents are adjustment-of-status eligible, you wouldn't even have to wait for the Form I-130 to be approved by USCIS, but could submit it to the agency concurrently with the Application to Register Permanent Residence of Adjust Status, or Form I-485. (If you have already gotten their I-130 approved, simply submit the approval notice, also called Form I-797, along with the adjustment of status packet.)
Many people hope that obtaining green cards for their parents will facilitate easy travel and long visits. Unfortunately, this strategy doesn't fit with U.S. immigration laws, which require that green card holders make their permanent home in the United States (although short trips to other countries are fine).
Contrary to popular myth, there is no minimum amount of time that a person can live in the United States to avoid issues of "abandonment of residence" here. If your parents leave the United States, even for a short time, and then upon return, U.S. border officials become convinced that their real home is outside the United States, the officials can deny their entry and revoke the green card (or at least place them into removal proceedings with that result).
Trips outside the U.S. of six months or longer are guaranteed to raise questions, and trips of a year or more raise a presumption that they have abandoned their U.S. residence.
Although it's possible to obtain family visas without professional legal assistance, your wisest course would be to consult with an experienced U.S. immigration attorney. The attorney can determine whether your parents are eligible for a U.S. green card and guide you in a timely manner through the appropriate application process.