"Cynthia has been my friend and colleague since we were little girls. I look forward to talking to her about her New York state gubernatorial bid," the actress said in a short statement to the New York Post on Wednesday.
Later, on Instagram, Parker made it clear that she supports her good friend.
"A mother An activist An advocate A fighter A NY'er A dear friend," she wrote alongside a photo of Nixon. "Running for Governor of our great state. My sister on and off screen, you have my love, support and vote."
Parker is the last of Nixon's co-stars from the successful HBO series to comment on her run for governor.
Kristin Davis tweeted on the day Nixon officially announced her campaign.
""I am so proud of @CynthiaNixon, no one cares more than she does about EVERY person getting a fair change and a good education. I know that she would be an excellent Governor!" she wrote on March 19.
Calling Nixon one of the most "intelligent and caring people in my life," Davis also tweeted that she had donated to Nixon's campaign.
Kim Cattrall was more reserved in her response to Nixon's announcement.
"I support & respect any former colleague’s right to make their own career choices," she tweeted in response to a follower's question.
In a video message on March 19, Nixon announced her primary challenge to New York's Democratic Gov. Andrew Cuomo. She has been an outspoken critic of Cuomo and his administration.
This would be Nixon's first bid at political office but she has long been an activist on political and social issues, particularly for LGBT and education issues. The actress, best known for her role as the practical lawyer Miranda on HBO's "Sex and the City," was born in New York.