Yes, you may be able to work in the USA while your green card application is pending, but you need legal authorization. If you are already in the U.S. and file for adjustment of status, you can apply for an Employment Authorization Document (EAD), which allows you to work legally until your green card is approved. If you’re outside the USA, you cannot work until you enter as a permanent resident or obtain a valid work visa. Unauthorized employment can negatively affect your immigration case.