After starting out at his hometown side Gaz Metan Mediaș, for which he amassed over 100 appearances in the Romanian top flight, Olaru transferred to FCSB in 2020.

[4] In early 2018, Olaru signed a precontract with fellow Liga I side FCSB, but the move initially fell through after a transfer fee could not be agreed upon.

[10] On 27 August 2020, Olaru made his debut in European competitions by starting and scoring in the 3–0 win over Shirak counting for the UEFA Europa League first qualifying round.

[16] Olaru received his first call-up for the Romania national under-21 team in September 2018,[17] and on 15 November that year scored in a 3–3 friendly draw with Belgium in Cluj-Napoca.

[18] He was subsequently selected in Mirel Rădoi's squad for the 2019 UEFA European Under-21 Championship, where he played two matches in the group stage and was an unused substitute in the 2–4 defeat to Germany in the semi-finals.

[19] Olaru's age also made him eligible for the 2021 edition of the European Championship, where head coach Adrian Mutu started him in all three fixtures of the group stage.

[20] Following Olaru's good display throughout the 2020–21 season, Mirel Rădoi—who was in the meantime promoted to the senior national team—handed him his full debut on 2 June 2021, in a 1–2 friendly loss to Georgia.