Colombian striker Valencia fired home a pass from Kalif Alhassan in the 53rd minute to sink the Canaries.
Ryan Bennett's mistake led to the goal as he gave away possession unnecessarily, allowing Alhassan to advance on goal before setting up Valencia.
It could have been different for the away side had new signing Nathan Redmond found the net with a long-range effort, but home keeper Milos Kocic tipped it onto the bar.
Carlo Nash made his debut in goal for City, while Steven Whittaker, Robert Snodgrass and Wes Hoolahan all started their first game of the tour.
The Norwich squad will now travel back to the UK ahead of a friendly with Brighton at the Amex Stadium on Tuesday.