The actress said she now understands why Michael Jackson chose to cover his kids' faces with masks "until they decided to be public".
"I want my daughter to live a normal life. I want her to feel free to be who she wants, so paparazzi stop taking pics of her! Enough!" Applegate tweeted.
"We need a law against this! Taking pics of kids is sick! When I chose to be an actor we didn't have paparazzi.
"We excelled on the merit of our work, not by what gown we were wearing. And those who use paparazzi to further their careers are going to have a rude awakening when their talent doesn't get them anywhere.
She added: "Just imagine for one second you having fun with ur kid in the park and a bunch of a holes start surrounding you and freaking ur kid out."
Applegate and musician fiancé Martyn LeNoble became parents to daughter Sadie Grace, their first child together, back in 2011.
The actress's latest show Up All Night was recently picked up by ITV2 in the UK, and she'll also return for the Anchorman sequel.