Sarah, who helped to guest edit the show, discussed subjects close to her heart during the live two-and-a-half show, including the importance of defibrillators, the best way to rehome a dog (she famously inherited the late Queen's corgis along with her ex-husband, Prince Andrew) and how to protect your skin.
While not every viewer was impressed – some described the appearance as "awkward" – most were thrilled to see the Duchess as a guest host.
"Such a shame it's one day only! The Duchess of York is fantastic on This Morning!" one fan wrote on social media.
"Love Sarah Ferguson. Breath of fresh air this morning," another agreed.
"How funny. I saw Sarah on Loose Women and thought she was great, very personable, funny and natural and hoped she would become a LW – so great to see her again on TV," a third commented.
At the start of the show, Sarah said: "I'm joining the family as co-host – fluff – alongside Alison and Dermot.
"And as guest editor for the day I've been working with the brilliant team behind the scenes to bring you some of the topics I’m most passionate about."
The programme's chef Marcus Bean also appeared to catch her eye, with Sarah quipping, "You’re very good looking," before adding, "I meant the carbonara."
As she and guest Gyles Brandreth went through stories in the newspapers, the discussion turned to I’m A Celebrity… Get Me Out Of Here!
Sarah was quizzed about whether she had been approached to appear on the show, and replied "every single year".
And when Dermot asked the Duchess what Christmas dinners were like with the royal family at Sandringham, she joked: "Beans on toast, Gyles over to you."
Ahead of the live show, the Duchess said in a statement: "I have appeared on This Morning before, but this time I am coming back in a very different role.
"I love live TV and am an enormous fan of the show, and the whole team is always lovely to deal with.
"I’m looking forward to being there for the whole morning, and thrilled to be guest editing the show which will mean getting to explore some topics that I’m passionate about."
This Morning’s editor Martin Frizell added: "We are all delighted Sarah, Duchess of York wanted to come back here and I’m very happy for her to make some of my decisions on Monday.
"She has a great understanding of the show and how television works and I feel viewers will be really interested in the running order she is putting together."
Sarah's presenting stint on This Morning comes after she appeared on Loose Women as a panellist earlier this month.
The Duchess, who is mother to Princesses Beatrice and Eugenie, underwent a single mastectomy in June following a breast cancer diagnosis.
She supported Loose Women's inaugural Don't Skip Your Screening campaign, as she opened up about her biggest fears after her diagnosis.
"The drive from the Royal Free Hospital, I'll never forget because of course your mind goes into, 'Oh my goodness, I've got to have a mastectomy,' and you look it up and it's all terrifying and 'this is what's going to happen' and then, 'I'm not going to see my grandchildren grow up'. That's what goes through your head," Sarah recalled.
"I almost missed the screening appointment that saved my life," she revealed, "I couldn't face a journey into London on a hot day this summer and it was only my sister Jane's insistence that I went, that persuaded me."