The law was introduced last May, stipulating that those born to undocumented foreign parents have to obtain residence permit needed to claim citizenship later. The deadline of February 1 has not been extended, meaning those who did not register will lose possibility of getting Dominican nationality.
"At the stroke of midnight the hopes of tens of thousands of vulnerable people will be scuppered as this deadline expires. This could leave thousands at risk of possible expulsion from the country," Erika Guevara Rosas, Americas Director at the rights watchdog, said.
"The simple fact is that when the vast majority of these people were born, the Dominican law at the time recognized them as citizens. Stripping them of this right, and then creating impossible administrative hurdles to stay in the country is a violation of their human rights," Guevara Rosas said.
Hundreds of thousands of individuals of Haitian origin reside in the Dominican Republic.
Descendants of Haitian immigrants born in Dominican Republic were previously recognized by the state, who issued their identification documents regardless of the migration status of their parents.