Hilary Duff said she was feeling stalked by a member of the paparazzi, including being followed as she attended her young son's soccer game and visited her sister at her home.
So Duff, who said she is nine months pregnant with her second child, turned on her own camera over the weekend and asked the man to stop.
"I've asked you once to leave me alone. Can you please stop taking my picture? You're like hunting me down," Duff said in a video she posted on Instagram, explaining that she is pregnant and sick.
She added: "I feel very uncomfortable. Please leave a pregnant woman alone."
When the photographer told her that he had "lost my whole morning" and had not gotten any pictures yet, she replied: "It's not my fault. Please leave me alone. It's the weekend, sir. Please."
Duff wrote on Instagram that the man had been tailing her the entire day.
"I politely asked him to let me be and he continues to follow and stalk me down like pray for hours now. This is not ok. I am 9 months pregnant," she wrote online.
"When people say that's what you get for signing up to be a celebrity it honestly makes me sick. This is every day of every month and it's simply not ok. If a non 'celeb' (I'm sorry to use that word) was dealing with this the law would be involved."
Duff, perhaps best known for her role in the sitcom "Lizzie McGuire," announced in June that she and her boyfriend, Matthew Koma, were expecting a baby girl.
Koma wrote on Instagram: "We made a baby girl! She will be as beautiful and sweet as her mother . . . @hilaryduff another incredible chapter begins."
Duff and her ex-husband, Mike Comrie, also have a 6-year-old son.
Duff is not alone. Many other celebrities have come face-to-face with unwanted photographers.
In May, Kristen Bell approached a paparazzo who had camped outside her children's preschool. The actress told "The Today Show" she blocked in the photographer's car and walked up to his window.
"Hi, my name's Kristen," she said she told him. "Do you realize how much you are putting my kids at risk? I have confidence your mom raised you better."
Bell told "Today" that she politely asked the photographer to delete the images - and he did.