The 82-year-old singer revealed in December he was set to have part of his lung removed after a "cancerous spot" was detected but he has now shared a brief update with fans to offer some reassurance.
Alongside a hospital selfie, Barry wrote on Instagram: "Better Today!(sic)"
One of his tour singers, Melanie Taylor, was among those to comment on the post.
She wrote: "That's my boss y'all! He's making it through the rain! Love you B!"
The Copacabana hitmaker revealed he had been diagnosed with lung cancer while cancelling his upcoming concerts.
In a post on Instagram, Manilow explained; "As many of you know I recently went through six weeks of bronchitis followed by a relapse of another five weeks.
"Even though I was over the bronchitis and back on stage at the Westgate Las Vegas, my wonderful doctor ordered an MRI just to make sure that everything was OK.
"The MRI discovered a cancerous spot on my left lung that needs to be removed. It's pure luck (and a great doctor) that it was found so early. That's the good news.
"The bad news is that now that the Christmas Gift Of Love concerts are over I'm going into surgery to have the (spot) removed."
However, Manilow explained the doctors do not think the cancer has spread so he's unlikely to require chemotherapy or radiation treatment following the operation.
He added: "The doctors do not believe it has spread and I'm taking tests to confirm their diagnosis. So that's it. No chemo. No radiation. Just chicken soup and I Love Lucy reruns."
Manilow will need a month to recover from the operation so had to call off his planned US shows in January.
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