The FA Cup final ended without incident as some 100,000 fans made their way home from Cardiff's Millennium Stadium.
A small group of Manchester United supporters held a protest ahead of the game over American businessman Malcolm Glazer's take-over of the club.
But the wet weather dampened down the expected demonstrations. Police had warned against protests in the stadium.
On the pitch, it was Arsenal who celebrated after a goalless match led to them winning 5-4 on penalties.
The match was the last FA Cup final to be held at Cardiff's Millennium Stadium.
Police were out in force before the game after some United supporters' groups said they would use the occasion to make their feelings known to a worldwide audience.
In the end, about 100 supporters, carrying a banner, chanted anti-Glazer songs as they marched towards the ground before kick-off. No trouble was reported.
Fans at the Millennium Stadium showed their anger at the takeover
South Wales Police said they were determined to head off any attempts to break out of the stands at the 72,500-seater stadium. Police leave in the city had been cancelled.
Cardiff Division commander Chief Superintendent Bob Evans had said police would not tolerate any form of demonstration inside the stadium, only lawful ones outside.
After the game, he said: "Everyone was in a fairly good mood. The rain has helped us - the best police officer in the world - and people have made their way to the stadium rather peacefully."
Around 25,000 United supporters attended the first FA Cup final clash with their London rivals since 1979.
Cardiff is a familiar destination for Arsenal fans - the side has made it to four of the five cup matches held in the city while the new Wembley stadium is being built.
The Millennium Stadium has become a popular destination with sports fans due to its city centre location, although this presents a particular challenge for police during tournaments.
There was a strong police presence in the city
Street sellers did a brisk trade in US flags to Arsenal supporters who chanted "USA, USA, USA" at United fans over the Glazer buyout.
Other traders did well selling black arm bands stamped with RIP in red letters at £3 each or £5 for two to United supporters.
Many United fans dressed predominantly in black, the team's colours on the day, but also to mark what an official at the Independent Manchester United Supporters' Association called "the funeral of Manchester United".
Street traders did well from the tension with the United supporters' camp.
One street trader, Martin Davies, from Gloucester, said: "I came with 300 arm bands and almost all of them have been sold.
"There's a few of us here and we've got 3,000 arm bands and 300 American flags and I expect they'll all be gone by the end of the day."
Both the Independent Manchester United Supporters' Association (IMUSA) and another supporters' group, Shareholders United, had called for mass demonstrations.