[1][4] He started his senior career, making his Divizia A debut on 15 September 1946, playing for ITA Arad in a 8–4 victory against Dermagant Târgu Mureș, by the end of the season making a total of 17 appearances in which he scored four goals which helped the club win the title.
[1][7][8] After one season, Mercea returned in Arad, winning the 1950 Divizia A title, being used by coach Francisc Dvorzsák in 22 matches in which he scored 12 goals, also scoring in the 1950 Cupa României final which was lost with 3–1 in front of CCA București.
[1][5][9] Mercea helped The Old Lady win the 1953 Cupa României, being used by coach Coloman Braun-Bogdan in the 1–0 victory in front of CCA București from the final, Braun-Bogdan also using him in 24 matches in which he scored once in the 1954 Divizia A season when he and the club won the fourth title together.
[1] Andrei Mercea played six matches and scored two goals for Romania's national team, making his debut on 6 June 1948 under coach Petre Steinbach in a 9–0 loss against Hungary at the 1948 Balkan Cup, a competition in which he would make two more appearances.
[12] He died on 24 January 2002 at age 76 and a book about him was written by Radu Romănescu, called Andrei Mercea – Campionul care desena inimi (Andrei Mercea – The champion that drew hearts), being released on 18 April 2018.