The actress is making a return to the BBC One soap to tie in with Peggy Mitchell's exit storyline, with Ross Kemp also reprising his role as Grant Mitchell.
Sharing a photo with her Twitter followers, Sam said: "First day back in Walford ... #Samisbackintown."
Posting the same snap to Instagram, she added: "First day back at work .. And loving every second."
Posing for a selfie this week, Danniella teased: "It's a Mitchell thing ... She's back .. Blonde & ready to rock Albert Sq #sammitchell."
Speaking about her return, Danniella previously said on Good Morning Britain: "I'm super excited to go back. I'm super excited to have the boys back together. Ross and Steve, and obviously Barbara, The four of us back together, the original Mitchells."
She also told Piers Morgan and Susanna Reid that she wants to make it a permanent return, while saying she hoped a familiar face would be joining her too.
"I'd love to come back full time," she revealed. "I'd like Darren Day to come in as my husband! That's what I'd like. I think he's a fabulous actor and I would love to see him in EastEnders. I think he'd fit right in."
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