Immigrant Witness and Victim Protection Act of 2018 This bill amends the Immigration and Nationality Act to eliminate the annual numerical limit on nonimmigrant U visas (victims of crime who are willing to assist law enforcement in investigations and prosecutions). The Department of Homeland Security shall grant work authorizations to aliens with a pending application for a nonimmigrant U visa or a T visa (victims of trafficking in persons who are willing to assist law enforcement in investigations and prosecutions). The bill prohibits, with specified exceptions, the following nonimmigrants from being considered inadmissible or subject to removal or deportation until there is a final denial of status application: a U or T visa applicant, a battered spouse seeking employment authorization, a battered spouse or child seeking permanent resident status, an alien seeking temporary protected status (TPS), or a self-petitioning alien seeking protections under the Violence Against Women Act.