In its survey released on Tuesday, Deloitte said the figure of 401.4 million had been helped by high broadcast revenue.
Real topped the "Football Money League" report, which ranks the 20 biggest clubs by revenue, for the fifth consecutive year.
European and Spanish champions Barcelona overtook Manchester United, who were hit by the weak pound, to move to second.
Barcelona posted the largest absolute increase in the Deloitte report, from the 2008-09 season. The club's revenue rose by 57 million euros to 366 million euros.
"Real Madrid and FC Barcelona have created a clear revenue gap between themselves and their European competitors, and look set to contest the top two positions in the Money League for the foreseeable future, particularly if the pound doesn't strengthen against the euro," Alan Switzer, director in the Sports Business Group at Deloitte, said in a statement.
Top clubs weathered the worst economic crisis in decades thanks to their loyal fan bases and large broadcast audiences, according to the report.
The combined revenue growth for the 20 clubs slowed compared with previous years to over 3.9 billion euros.
"However, it will not be until 2009-10, the season currently in progress, before we see the full impact on clubs' revenues," said Paul Rawnsley, director in the Sports Business Group at Deloitte.
The top 20 was little changed from last year, with Werder Bremen and Manchester City replacing VfB Stuttgart and Turkish club Fenerbahce.
The list was again dominated by European clubs, with seven English clubs, four from Italy, and two each from France and Spain. The number of German clubs grew to five from four.
MILAN, March 2 (Reuters) - Real Madrid and Barcelona topped the world's richest club followed by Manchester United, according to an annual survey by accountancy firm Deloitte released on Tuesday.
The combined revenues of the top 20 clubs grew by 26 million euros ($35.16 million) to over 3.9 billion euros in 2008-09, amid the global economic downturn.
Top 10 clubs by revenues featuring in the latest Deloitte "Football Money League."
(All 2008/09 figures in million euros, previous position in brackets).
1 (1) REAL MADRID
Revenues: 401.4 (from 365.8)
Matchday: 101.4
Broadcasting: 160.8
Commercial: 139.2
2 (3) FC BARCELONA
Revenues: 365.9 (from 308.8)
Matchday: 95.5
Broadcasting: 158.4
Commercial: 112.0
3 (2) MANCHESTER UNITED
