The 25-year-old British singer showed his support for his One Direction bandmate Monday on Twitter following the release of Horan's solo single "Too Much to Ask."
"Niall you sound great on the new single lad. Big tune. Love the production!! @NiallOfficial," he tweeted. "Effortless and really well written! Buzzing for you Nialler."
Horan responded to Tomlinson's praise by writing, "thank you tommo, love ya." He had thanked his 34 million followers for their support in a tweet earlier in the night.
"Thank you to all of you for the lovely support for 'too much to ask.' If you haven't heard it yet, take a list," the star wrote.
Horan released "Too Much to Ask" last week following the debut of "Slow Hands" and "This Town." The songs will appear on his debut solo album, Flicker, which is scheduled for release Oct. 20. He will promote the record with a new tour in 2018.
"Can't wait to get back on the road & play this album for you," the singer announced last week. "And... my good friend the incredible @MarenMorris is joining me for all of it."
Horan and Tomlinson last performed with One Direction in December 2015. The British boy band has been on hiatus since as Horan, Tomlinson, Harry Styles and Liam Payne focus on their personal lives and solo careers.