The 46-year-old actress was joined by her brother Gerry.
“So proud of my brother Gerry,” she tweeted. “Thank G. For running next to me today- love you lots.”
In addition, Anderson raised nearly $76,000 for the J/P Haitian Relief Organization in order to aid the impoverished Caribbean nation affected by the 2010 earthquake.
She also revealed she had considered putting on her Baywatch suit for the marathon.
“I had friends ask me to [wear it]. They think it would be really funny,” she told ESPN. “The bad thing was, I did think twice about it!”