Since the summer of 2007, Walsh has been the spokesperson for Narcolepsy Network, working to promote national awareness of narcolepsy through infomercials and DVDs.
In January 2008, Walsh participated in a video for Democratic presidential candidate Barack Obama called, "Yes We Can", produced by will.i.am of The Black Eyed Peas. She also campaigned for Obama in Arizona, Texas, Nevada, and Pennsylvania.
In July 2008, Walsh was nominated as a candidate on the Unite for Strength slate for a place on the national governing board of the Screen Actors Guild (SAG) in elections scheduled for 18 September 2008. On September 18, 2008, Walsh was elected to serve on the SAG board for a three year term. Walsh ran as a candidate with the Unite for Strength party who won 6 of the 11 Hollywood Division seats which were up for contention in the recent Screen Actor's Guild National Board elections.
Walsh supports pet adoption and frequently campaigns for the cause. On February 7, 2008, she cut the ribbon to a new dog adoption center named Pedigree(R) Dogstore in Times Square.
In 2005, Walsh joined the Planned Parenthood Federation of America (PPFA)'s Board of Advocates, and in 2008 received the PPFA Maggie Award for an Artist who Stands Up for Reproductive Health and Freedom. Kate has participated in numerous Planned Parenthood activities, including national fundraisers, local Planned Parenthood affiliate events, the PPFA Awards Gala, and lobby day on Capitol Hill promoting the need for comprehensive sex education. In January 2009, Kate spoke at the Planned Parenthood Presidential Inauguration Brunch in Washington, DC.
As announced in late 2009, Walsh partnered with the ocean conservancy and advocacy group Oceana to call for increased sea turtle protections. She joined experts from the group on a trip to the Virgin Islands to witness the turtles' hatching and moving to the sea. In her own words: "I want to get the word out and make people aware about the challenges facing sea turtles. I also want to help get legislation enacted to keep harmful fishing techniques to a minimum and help protect the sea turtles."
Walsh referenced Oceana during a September 16, 2010 appearance on the Tonight Show with Jay Leno. She told Leno that her dress was covered in sushi and sashimi as an homage to a dress made of beef worn by Lady Gaga at the 2010 MTV Video Music Awards. While she claimed it was sustainable seafood, Walsh later admitted via her twitter account that the sushi was fake.
She recently attended a meeting on Capitol Hill in which they marked the one year anniversary since the BP oil spill.