The solo artist and former One Direction star posted the news from his official social media accounts in the evening of 28 February.
“Due to the recent events in Ukraine, I have to sadly announce that my tour shows in Moscow and Kyiv are cancelled until further notice,” he wrote.
“The safety of my fans is my priority and my thoughts go out to the people of Ukraine and all those suffering from this needless war.”
Tomlinson was due to play in the Crocus City Hall in Moscow on 6 July, and the Stereo Plaza venue in Kyiv two days before.
The 30-year-old musician joins a growing number of artists to cancel shows in Russia, amid the ongoing invasion of Ukraine.
Green Day announced on Instagram on Sunday 27 February that they were cancelling a planned Moscow gig.
Other music artists including Imagine Dragons and Franz Ferdinand have cancelled their concerts in Russia.
The Eurovision Song Contest announced last week that Russia will be banned from performing at the 2022 competition.
“The decision reflects concern that, in light of the unprecedented crisis in Ukraine, the inclusion of a Russian entry in this year’s contest would bring the competition into disrepute,” said the European Broadcasting Union in a statement.
The decision constituted something of a U-turn, with the ceremony’s organisers previously being met with a barrage of criticism for announcing that they had no plans to prevent Russia from taking part, despite being urged by Ukraine’s public broadcaster.
Follow live updates on the Ukraine-Russia conflict here.