"Hello Twitter! Hold on to your hats. I'm ready to tweet everything from anywhere to anyone who gives a damn!" Stritch said in her first tweet.
"Once someone explained to me what Twitter is, I was happy to be a Twittee. How nice to be able to share my experiences," she said in a separate statement.
Twitter's Lara Cohen said she is "thrilled to have her" and Cohen's entire team is eager to welcome her to the Twitterverse.
The documentary "Elaine Stritch: Shoot Me" is set for release Feb. 21.