The 'Rolling in the Deep' singer called the X Factor contestant "incredible" while watching tonight's show (October 13).
"Ella Henderson on X Factor is absolutely incredible! I LOVE her!! Good luck xx," Adele tweeted.
Henderson, who performed her own song at her first audition, has often been compared to Adele. She sang 'Lovin' You by Minnie Riperton on tonight's show.
Nicole Scherzinger called Henderson "timeless" and "classic", while Louis Walsh said she could be a "worldwide recording artist". He also claimed that mentor Tulisa Contostavlos was trying to style the 16-year-old like Adele.
Digital Spy readers voted Henderson as their favourite X Factor act following the first live show last week.
Watch Ella Henderson singing 'Lovin' You' on tonight's show below: