Her tweet on Saturday is the first time Yaccarino has spoken publicly since the news broke on Thursday that she was in talks to become the next CEO of Twitter.
Musk, who has served as CEO since his $US44 billion buyout of Twitter last October, announced her appointment on Friday.
"I've long been inspired by (Musk's) vision to create a brighter future. I'm excited to help bring this vision to Twitter and transform this business together!" Yaccarino tweeted.
Yaccarino, who as advertising chief for NBCUniversal spent several years modernising its ad business, said she was committed to Twitter's future, and said user feedback was vital to build Twitter 2.0.
She will take over a social media platform that has been trying to reverse a plunge in ad revenue and is beset with challenges, along with a heavy debt load.
Since Musk acquired Twitter, advertisers have fled the platform, worried that their ads could appear next to inappropriate content after the company lost nearly 80 per cent of staff. Musk earlier this year acknowledged Twitter had suffered a massive decline in ad revenue.
While Musk said Yaccarino would help build an "everything app", which he has previously said could offer a variety of services such as peer-to-peer payments, his selection of an advertising veteran signalled that digital ads would continue to be a core focus of the business.
Musk has long said he intended to find a new leader for Twitter.
Musk, who is also the CEO of electric-vehicle maker Tesla, on Friday said that bringing Yaccarino on as Twitter's new chief will help him devote more time to Tesla.
