Joosten, who most recently played Karen McCluskey in "Desperate Housewives," was with family and friends when she died in Westlake Village, Calif., People magazine reported.
"Kathryn passed away this morning after a valiant fight against her cancer," Nadine Jolson, Joosten's representative, told E! News. "This is a terrible loss, and she fought as hard as she could."
Her family noted in a statement that Joosten had fought lung cancer for 11 years.
"Thanks to everyone for their love and support," her family said. "We are laughing through our tears. We love you, Kathy, thanks for everything."
Joosten, who won Emmys in 2005 and 2008, took up acting at age 42 after a career as a psychiatric nurse.
"Desperate Housewives" creator Marc Cherry said Joosten's character initially had been intended to appear in just one episode.
"We then cast Kathryn Joosten and she infused the part with so much feisty wit and curmudgeonly bravado, we knew we had to move her onto Wisteria Lane for the run of the series," Cherry said. "I will forever miss her, as a co-worker and as a friend."
Joosten also appeared on "Dharma and Greg," "My Name is Earl," "Ally McBeal" and "The West Wing."