Shaw PR took African Aids Action to court after the Essex-based registered charity failed to pay for the agency's work.
Founder George Shaw and his team worked for the charity last November and December, securing newspaper coverage ahead of World Aids Day.
In court, African Aids Action director Eyob Ghebre-Sellassie claimed the work had been done pro bono, but did not produce evidence of any such agreement.
'Although all fees were confirmed in writing and accepted in an exchange of emails by Ghebre-Sellassie, his only defence was that he had not fully read the documentation,' said Shaw. 'He could not produce any evidence disputing an unpaid invoice until after court papers were served.'
Shaw said he took legal action as a warning to other marcoms companies that may be approached by the charity. The charity's website displays quotes from politicians including Tory MP Alan Duncan and Labourite Hilary Benn. The charity said it was appealing against the ruling.