According to Maksym Kozytskyy, Jolie - who has been a UNHCR special envoy for refugees since 2011 - had come to speak with displaced people who have found refuge in Lviv, including children undergoing treatment for injuries sustained in the missile strike on the Kramatorsk railway station in early April.
The attack in the eastern Ukrainian city appeared to deliberately target a crowd of mostly women and children trying to flee a looming Russian offensive, killing at least 52 and wounding dozens more.
"She was very moved by (the children's) stories," Kozytskyy wrote.
"One girl was even able to privately tell Ms Jolie about a dream she'd had."
He said Jolie also visited a boarding school, talked with students and took photos with them, adding "she promised she would come again".
According to Kozytskyy, Jolie also met with those arriving at Lviv's central railway station as well as with Ukrainian volunteers providing the new arrivals with medical help and counselling.
"The visit was a surprise to us all," he wrote.
"Plenty of people who saw Ms Jolie in the Lviv region could not believe that it was really her. But since February 24, Ukraine has shown the entire world that there are plenty of incredible things here."
AAP with The Project