A man under 20 years old hit about ten people with eggs before being captured by the police.
At least one young woman was hit in the head.
The man had an accomplice, who managed to escape. The caught perpetrator admitted planning and carrying out the egg attack.
Lauri Ahonen, who took part in the parade, said the man struck and kicked at least one person who tried to stop him, before being finally captured.
Two years ago the Pride Parade suffered a gas-attack. Three men were later convicted of the attack, and were given suspended prison sentences.
Highlighting the rights of sexual and transgender minorities, Helsinki Pride is celebrated every year over one week.
The police estimate that this year's Pride Parade attracted between 7,000 and 8,000 participants.