The Traveller Movement said the group was denied entry at The Coronet on Holloway Road in November 2011.
At the Central London County Court, the judge ruled there had been direct discrimination.
Pub owner Wetherspoon had denied allegations of racial discrimination.
Eight of the claimants were successful and were awarded £3,000 each by the judge.
In the judgement, Judge Hand QC said the thinking of the then manager of the pub was "suffused with the stereotypical assumption that Irish Travellers and English Gypsies cause disorder wherever they go".
The judge added: "In my judgment this is racial stereotyping of those with that ethnic origin.
"It can be reduced to this crude proposition: whenever Irish Travellers and English Gypsies go to public houses, violent disorder is inevitable because that is how they behave".
Martin Howe, a solicitor who acted for the travellers, said: "This judgment will shake to the core all those who engage in racist conduct towards Irish Travellers and Romany Gypsies.
"The last bastion of 'acceptable racism' has come crashing down."
The Traveller Movement, which was then known as the Irish Traveller Movement in Britain, had argued that a group of 15 attending its annual conference was discriminated against.
The group, including travellers, a police inspector, a barrister and a priest, was denied entry to the pub - which was next door to the event.
The pub manager refused entry to groups of delegates, saying he was concerned there might be trouble because the conference was focusing on evictions from the Dale Farm traveller site in Essex.
Tim Martin, chairman of Wetherspoon, said: "Wetherspoon apologises to the eight individuals who were denied entry and for any upset and distress this caused to them.
"In the light of the judgment, although we have always been fully committed to operating our premises in a non-discriminatory way, we will undertake a full review of our relevant policies, procedures and training."
Some £24,000 in damages has been awarded to a group attending an Irish Travellers conference after they were discriminated against by the owners of a north London pub.