The competition began with a league stage.[4] The draw for the first two rounds was held in June 2021, with the identity of the 2020 Championship winner still unknown, a first such event in the competition's history.[5]
The Round 3 draw was made on 26 September, giving the following fixtures: Ard an Rátha v Kilcar, Seán MacCumhaills v Réalt na Mara, Naomh Conaill v Termon, St Naul's v Glenswilly, Gaoth Dobhair v Glenfin, Na Cealla Beaga v Milford, St Eunan's v Aodh Ruadh and Four Masters v St Michael's.[7]
The Round 4 draw was made in early October, giving the following fixtures: Kilcar v Gaoth Dobhair, Aodh Ruadh v Ard an Rátha, Réalt na Mara v St Eunan's, Termon v Seán MacCumhaills, Glenswilly v Naomh Conaill, St Michael's v Na Cealla Beaga, Glenfin v Four Masters and Milford v St Naul's. Three clubs had by then advanced to the knockout stages – Gaoth Dobhair, Kilcar and Naomh Conaill. Going into Round 4, played on the weekend of October 9, St Eunan's, Glenswilly, St Naul's, St Michael's and Aodh Ruadh sat in the remaining five places.[8]
Gaoth Dobhair and Naomh Conaill, the last two clubs to win the competition, were paired with each other in the quarter-final draw. Seán MacCumhaills and Kilcar met in the other quarter-final on that side of the draw. On the other side of the draw St Eunan's and St Naul's played each other in one quarter-final, while St Michael's and Aodh Ruadh played each other in the other quarter-final.[10]
16 October 2021 Quarter-final
Kilcar
1–17 — 0–02
Seán MacCumhaills
Pearse Memorial Park, Ardara Referee: Jimmy White (Killybegs) Man of the Match: ???
The semi-final meeting of Kilcar and Naomh Conaill was shown live to a national audience on TG4.[11] Naomh Conaill won, after a late Patrick McBrearty goal that would have brought the sides level, was ruled out.[12]
23 October 2021 Semi-final
St Eunan's
0–10 — 0–05
St Michael's
MacCumhaill Park Referee: Mark Dorrian (Gael Fhánada) Man of the Match: ???
It was Naomh Conaill's fifth consecutive appearance in the final.[10] The game was televised live on TG4.[12] A minute's silence was held before the game in memory of Martin Griffin, whose sudden death occurred the previous day.[1][13]St Eunan's won.[1]
Eight clubs (Glenfin, Glenswilly, Réalt na Mara, Ard an Rátha, Milford, Na Cealla Beaga, Termon and Four Masters) entered the draw for the relegation play-offs once the quarter-final line-up was confirmed.[9]
Watty Graham's knocked St Eunan's out of that competition with an injury time point from Danny Tallon winning the game at O'Donnell Park, despite St Eunan's scoring the only goal and leading for much of the game and Shaun Patton saving a penalty.[14]
^ abBonner, Declan (16 December 2021). "Huge opportunity for Downings this weekend: Under 21 Final". Donegal News. p. 71. A special mention has to go to Shane O'Donnell, who scored 1–3 last Sunday [in the Under 21 Final]. I don't know if anyone has ever won man-of-the-match in a senior county final and in an Under 21 final in the one year before. It is a remarkable achievement.
^ abMolloy, Edward (18 November 2021). "Donegal Senior Club Championship Scorers 2021". Donegal News. p. 66. Total Scored in 2021 Championship 82–1001 (1247pts) 2020 total was 98–956 (1250pts) Total games played = 46 (42 in 2020) Scoring average per match = 27.1pts (29.76pts in 2020) Total number different scorers = 226 + 2 Own goals by opponents (201 in 2020) Top scoring goalie is again Andrew Walsh Glenfin 0.04 Seven of last year's players feature this year in scoring charts. Six of current county senior panel make the [2021] list. [Ed: These seem to have been M. Murphy, O. Gallen, N. O'Donnell, P. McBrearty, M. Langan and P. Mogan, in descending order with 'Top 18 Scorers' given by Edward Molloy for 2021].
^"Aodh Ruadh club notes". Hogan Stand. 7 September 2021. Aodh Ruadh make their long-awaited return to senior championship this weekend. Four Masters will be the opposition for both our seniors and reserves. The seniors take on the Donegal town men in Tir Chonaill Park on Sunday at 2pm, with that game being followed by the reserves at 3.30pm.
^ abCraig, Frank (21 October 2021). "'This is where we want to be' — McNulty". Donegal News. p. 60. With fireworks expected to fly, it's no surprise that the live TG4 cameras are rolling into Letterkenny on Sunday for what is being billed as a grudge match between the two form sides in this year's Donegal SFC.