Oļegs Sišļaņņikovs is a product of the HS Riga hockey system, where he progressed through both the youth and senior ranks. Since the 2017/18 season, the forward has built an international career, playing for Kitzbüheler EC in Austria, Ritten/Renon in Italy, Hull Pirates in the United Kingdom, Donbas Donetsk in Ukraine, Gap in France, and HYC Herentals in Belgium, where he spent the previous two seasons.
Sišļaņņikovs has represented Latvia at the U18 and U20 national team levels. His achievements include a gold medal at the IIHF U20 World Championship Division IA, an Italian league title and Super Cup, as well as one gold and one silver medal in the Ukrainian championship.
Ahead of the 2026/27 season, Oļegs Sišļaņņikovs joined Kyiv Capitals.
