Olexandr was born in Kryklyvets (Vinnytsia region). His first team was BRW-BIK Volodymyr-Volynskyi. First coach – Ruslan Gan.
He joined FC Dynamo Kyiv in 2013.
Tymchyk made his debut in Ukrainian U-19 League on April 9 2014 – in Dynamo home fixture against FC Metalurh Zaporizhia youngsters (2:1). He scored his first goal for this team on August 26 2015 – against FC Shakhtar Donetsk (2:0).
On October 18 2014 he played the first game for Dynamo U-21 – against FC Hoverla Uzhhorod (2:2). On August 6 2016 Olexandr scored the first goal for our youth team – against FC Dnipro (2:0).
He played his first match in UEFA competitions on September 16 2015. It was the UEFA Youth League home fixture against FC Porto (2:1).
On October 26 2016 Tymchyk made his debut for FC Dynamo Kyiv first team – in the Ukrainian Cup round of 16 against FC Zoria Luhansk (5:2).