[2] Sean Fitzharris also went to the First Division as he joined Morton[3] On 1 July, Celtic confirmed the signings of Adam Matthews from Cardiff City,[4] Kelvin Wilson from Nottingham Forest[5] and Dylan McGeouch from Rangers.

[14] On the same day Celtic officially signed Victor Wanyama from Belgian Pro League club K. Beerschot AC on a four-year deal.

[19] Due to the fact that the 2011–12 Scottish Premier League started several weeks earlier than usual, Celtic's first competitive match came on 24 July.

Goals from Ki Sung-yueng and Anthony Stokes secured victory over Hibernian, although Gary Hooper also missed a penalty in the match played at Easter Road.

[22] Celtic then finished second in the 2011 Dublin Super Cup after losing 2–0 to Inter Milan on 30 July and beating a League of Ireland XI 5–0, the next day.

[24] The next day Darren O'Dea signed for English Championship side Leeds United on a season long loan.

[28] On 17 August, Fraser Forster joined on a loan deal from Newcastle United, having spent the previous season as first choice goalkeeper at Celtic.

[29] On 21 August, Celtic suffered their first home defeat to St Johnstone since 1998 when Dave Mackay scored to give the away side a 1–0 victory.

As a result of this Celtic were awarded both matches as 3–0 wins[38] and took Sion's place in the group stage along with Atlético Madrid, Udinese and Stade Rennais.

[39] On 5 September, Morten Rasmussen joined Turkish Süper Lig side Sivasspor, on a short-term loan, until December.

Rennes led 1–0 at half-time after a mix-up between Cha Du-ri and Fraser Forster, but Joe Ledley scored in the second half with a header to secure a draw.

[51] Celtic then won four Scottish Premier League ties in November, defeating Motherwell 2–1,[52] Inverness Caledonian Thistle 2–0,[53] Dunfermline 2-1[54] and St Mirren 5–0.

A solitary goal from Gary Hooper in the first half was enough to defeat Dundee Utd[58] whilst a Victor Wanyama strike from 25 yards saw off the challenge of Hearts at Celtic Park the following week.

[59] Celtic travelled to Italy to face Udinese in the UEFA Europa League and claimed a 1–1 draw, a result which meant they would exit the tournament at the group stages.

Win Draw Loss *Celtic were awarded the match after Sion had fielded ineligible players and were disqualified from the Europa League by UEFA.