|2nd Copa del Rey|
|Defending champions||Athletic Bilbao (2nd title)|
|Runners-up||Club Español de Madrid|
|Goals scored||15 (5 per match)|
Originally, three teams were to participate, one for each region. The newly formed Madrid Football Federation, who organized the competition for the first time (the previous tournament was organized by Madrid CF), invited Athletic Bilbao representing Biscay and Espanyol of Barcelona representing Catalonia. Madrid was to be represented by the winner of a preliminary round between Club Español de Madrid and Madrid-Moderno (a merger of Madrid CF and Moderno). The three teams were to contest the cup in a round-robin format.
Before the tournament Espanyol, unhappy with the competition system, announced they would not go to Madrid. Then two more teams from Madrid, Moncloa FC and Iberia Football Club, were admitted in the competition, forcing a change to the schedule.
The competition started on March 13, 1904, but on March 19 the problems started. The match between Español of Madrid and Madrid-Moderno ended tied at 5–5. The captains of both teams agreed not to play extra time, but failed to reach an agreement on when they should replay the match. Español wanted to play the next day, but Madrid-Moderno refused, saying that under the rules of the tournament a replay could not be played less than 48 hours after the previous game. Next day Español went to play the replay, but Madrid-Moderno did not. The regional federation, whose president Ceferino Birdalone happened to be president of Español as well, ruled in favor of Español, who were declared winners of the match.
While the Cup final was originally scheduled for March 26, the inclusion of Moncloa and Iberia in the tournament at the last minute necessitated an extra qualifying game and delayed the final. On March 27, Español and Moncloa faced one another. Español were winning 1-0 when by chance their defender Hermúa was injured. He was diagnosed with a broken tibia and fibula. The referee then decided to suspend the match, at which point Español claimed the victory. During a meeting of the Madrid Association of Football Clubs, the president of the organization proposed to accept the claim, but as he was as Chairman of the claimant club his proposal was rejected.
To resolve the conflict, a lottery was held, which favored Español, and named them as finalists. But this team had not won the regional heats: they had tied one game and had not completed the other, which led Athletic to file a complaint. Faced with this problem and unable to quickly solve the case, coupled with the rush of players from the Basque club to return to their occupations, the Madrid Association decided to award the cup to Athletic as defending champions.
Madrid Qualifying TournamentEdit
|Club Español de Madrid||5–5||Madrid-Moderno|
Antonio Alonso 
Replay not played. Español declared winners.
Match abandoned at 1-0. Español declared winners.
Final Copa del ReyEdit
The qualification of Español was disputed. Athletic, who were not required to qualify, were declared winners.
|Copa del Rey 1904 Winners|