The defender impressed, forming a solid partnership with Turkish defender Caglar Soyuncur in the heart of defense to stop City from scoring.
Amartey, who missed the FA Cup final, proved he could be an important player for the Foxes in the upcoming season.
The FA Cup winners snatched a late victory after Nigerian forward Kelechi Iheanacho climbed off the bench to score from the spot for Leicester.
Ihenacho won the penalty in the 88th minute before converting to secure the Shied for his club.
Leicester City begins their English Premier League campaign with a home game against Wolverhampton Wanderers on August 14, 2021.