Salah slams 'harsh' Liverpool fans for jeering Alexander-Arnold
Alexander-Arnold is widely expected to join Real Madrid once his contract expires in June.
The England right-back, who revealed his decision to quit his boyhood club last week, was jeered by Liverpool supporters when he came on as a second-half substitute in Sunday's 2-2 draw against Arsenal at Anfield.
Salah said on Friday that he was saddened by the taunts aimed at Alexander-Arnold, who has two games left as a Liverpool player against Brighton on Monday and Crystal Palace on May 25.
"Absolutely. I was surprised because this is not how we act as Liverpool fans," the Egypt forward told Gary Neville in a Sky Sports interview.
"I think somehow the fans were being harsh with him. I think he didn't deserve it at the time, he deserved the fans to treat him the best way possible because he gave it all to the fans."
Salah was also involved in a prolonged contract saga this season, but eventually committed his future to the Reds by signing a new two-year deal.
Calling for Liverpool fans to give Alexander-Arnold a more respectful farewell in his last two games, Salah said: "Imagine someone who gives you his all for 20 years. It's shouldn't be like this.
"I hope that will change next game, against Brighton or in the last game of the season, because he deserves the farewell."
Liverpool-born Alexander-Arnold, who made his first-team debut in 2016, has made 353 senior appearances for Liverpool in all competitions, scoring 23 goals.
The 26-year-old has won two Premier League titles, the Champions League, the FA Cup and the League Cup with the Reds.
Salah admitted it will be emotional to say goodbye to one of his close friends when the season ends.
"I told him yesterday don't give me eye contact in your farewell. I really love him. I think he deserves the best farewell leaving the club," he said.
"He has done a lot for the city and done a lot for the club and he's one of probably the best players in the club's history. He gave it all.
"I think he needed a new challenge. He spoke to me about it. It's his decision for sure. He's 25, 26 years old and won it all twice or three times. What more can he have done?"