Johnson wrote alongside the video on Twitter: “This week I visited Ukrainian troops training for the British Armed Forces in North Yorkshire.
“The UK is committed to doing everything possible to help Ukraine continue to repel Russian aggression.”
He was also seen observing military training exercises and addressing troops while standing in front of combined Ukrainian and British flags.
It is the prime minister’s second military getaway of the week, after taking a ride in a Typhoon fighter jet on Monday.
Johnson was visiting RAF Coningsby for a behind-the-scenes look at one of the RAF’s two rapid reaction warning stations, which protect UK airspace.
The base is home to two front-line combat-ready squadrons and the training station for Typhoon pilots.