Horner was dismissed by the F1 team after 20 years as its figurehead last July but the four-time world champion has revealed that he speaks to his ex-boss "every week".
Asked if he still talks to Horner, Verstappen told Viaplay: "Every week, every race. On Friday, Saturday and Sunday and usually via text message. But also on holiday, for example. Every week.
“Of course he knows everyone in the team, but it's more about 'I wish you good luck' and 'I believe in you' - biggest fan.
"What we've all been through. But also, 'You know you can do it.' You know, all that kind of stuff and outside of that, of course, you talk about things other than racing too. Yes, every week. Every race weekend. Even after his contact."
Verstappen's form improved significantly after Laurent Mekies took charge at Red Bull during the second half of the 2025 campaign and the Dutch driver indicated that the decision to axe Horner was correct.
The 71-time Grand Prix winner - who was pipped to the title by McLaren's Lando Norris last year - said: "The team is doing well. We have a lot of confidence. You see people smiling, it's a nice environment, everyone gets along well and we missed that at one point. The Red Bull style was a bit lost or gone."
Verstappen added: "Things weren't going very well for the whole team.
"In terms of results, there was a bit of unrest in the team and when things haven't been going well for a long time...in the end, the shareholders also wanted change because they weren't happy with how things were going either."