The 26-year-old confirmed that his time at Liverpool will conclude this summer in an emotional video on Monday as his contract slowly runs down.
Liverpool were unable to convince the homegrown talent to extend his highly successful career at Anfield, and now he looks certain to join Real Madrid for free in the next few months.
Henderson, who spent several years with the defender, has now replied to the emotional video on Instagram, wishing him all the best for the future.
"What a journey! It's been amazing to see you grow as a player and a person over the years.
"Thank you for everything, and good luck with the next chapter.
"Just keep being you and challenging yourself every day! The scouser in our team!"
The England midfielder made the controversial decision to leave Anfield for Saudi Arabian side Al Ettifaq at the end of the 2022/23 season.
Henderson is a player for whom Liverpool fans have mixed feelings, despite him captaining the side to the Champions League and Premier League titles in 2019 and 2020, and he will have been a leader to Alexander-Arnold during his time at the side.
Alexander-Arnold has gone on to make 352 appearances for his boyhood club, scoring 23 goals and winning the Champions League, two Premier League titles, the FA Cup, League Cup, Club World Cup and UEFA Super Cup.
Much like Henderson, he will be viewed differently when he leaves, especially for free to one of the club's biggest rivals.