It had been an evenly-matched affair in front of a crowd of 18,032 at Pittodrie, until Nouioui stroked home after Victor Wanyama’s powerful strike had crashed back off the post.
Mulgrew added a second goal four minutes later, acrobatically sending a ball from Georgios Samaras past his former Dons team-mate Jamie Langfield.
Celtic had gone three games without a win in the SPL, losing to Kilmarnock before draws against Dundee United and St Johnstone, so Ambrose was delighted to return to winning ways. The Nigerian said: “To get back to winning is a great feeling. The past two or three games in the league have not been good for us. We’ve lost points and conceded goals, but this is football.
“We had to be patient and take our chances when they came. The manager asked us to be patient, because the goals would come, even if it took until the 95th minute.”