Ionescu berkompetisi di [[Olimpiade Musim Panas 2016]] di [[Tenis meja di Olimpiade Musim Panas 2016 - Tunggal putra|tunggal putra]], di mana ia tersingkir di babak ketiga oleh [[Marcos Freitas]].<ref>{{cite web|title=Ovidiu Ionescu |url=https://www.rio2016.com/en/athlete/ovidiu-ionescu |website=Rio 2016 |access-date=28 August 2016 |archive-url=https://web.archive.org/web/20160828155022/https://www.rio2016.com/en/athlete/ovidiu-ionescu |archive-date=28 August 2016 |url-status=dead }}</ref><ref>{{cite web|title=Men's Singles – Standings |url=https://www.rio2016.com/en/table-tennis-standings-tt-mens-singles |website=Rio 2016 |access-date=28 August 2016 |archive-url=https://web.archive.org/web/20160827014737/https://www.rio2016.com/en/table-tennis-standings-tt-mens-singles |archive-date=27 August 2016 |url-status=dead }}</ref>
Pada September 2018, Ionescu mencapai final pertamanya [[Kejuaraan Tenis Meja Eropa 2018|Kejuaraan Eropa]] tetapi kalah dari unggulan No. 1 [[Timo Boll]]. Ia mengalahkan pemegang gelar kontinental [[Emmanuel Lebesson]] di babak kedua, unggulan ke-6 [[Jonathan Groth]] di babak 16 besar, unggulan ke-9 [[Vladimir Samsonov]] di perempat final dan unggulan ke-8 [[Kristian Karlsson]] di semifinal.<ref>{{cite web|url=https://www.ittf.com/2018/09/22/pride-restored-ovidiu-ionescu-upholds-national-honour/|title=Pride restored, Ovidiu Ionescu upholds national honour|publisher=[[International Table Tennis Federation]]|date=22 September 2018}}</ref><ref>{{cite web|url=https://www.prosport.ro/alte-sporturi/alte-sporturi/ovidiu-ionescu-argint-istoric-la-campionatele-europene-de-tenis-de-masa-romanul-a-cedat-in-finala-cu-germanul-timo-boll-scor-4-1-17529627|title=Ovidiu Ionescu, argint istoric la Campionatele Europene de tenis de masă|publisher=[[Prosport]]|date=23 September 2018|language=ro}}</ref>
