The proclamation was made by San Diego mayor Kevin L. Faulconer, who said Nisha was recognised for her contributions in the fight for transgender rights.
Last week, Nisha was one of the 14 recepients of the US Secretary of State’s International Women of Courage Award in Washington D.C.
April 5 also happens to be the activist's birthday.
Nisha, who is still in the United States, said in a Facebook post that the proclamation was like a dream come true for her.
"A day was made for me in San Deigo and it's also my birthday," she wrote.
Nisha also received the Jose Julio Sarria Civil Rights Award from San Deigo City commissioner Nicole Murray Ramirez.
She was also recipient of Human Rights Watch’s Alison Des Forges Award in 2015.
Nisha, 36, became a transgender rights activist after going through the harrowing experience of being sexually abused when she was thrown into a male prison for dressing as a woman in 2005.
She leads Seed Foundation, which offers lifelines to transwomen, sex workers and HIV patients in the Chow Kit area.