"Officers once again took a measured approach and tried to engage the group to disperse. They clearly had no intention of doing so, and so it did result in 19 people being arrested, and a further ten being issued with a fixed penalty notice", he said.
The United Kingdom eased coronavirus restrictions on 13 May, allowing people from two households to meet in parks, but larger gatherings are not permitted.
Police said that, while most people were compliant with the guidance, a "relatively small group" in Hyde Park came together to protest in clear breach of the rules, putting themselves and others at risk of infection.
Earlier in the day, the brother of former Labour leader Jeremy Corbyn was arrested at in Hyde Park after he gave a speech with a megaphone.
The UK has been on lockdown to slow the spread of coronavirus since 23 March, with people urged to stay at home as much as possible and many businesses and services shut down temporarily.
As of 16 May, more than 240,000 people have tested positive for the novel coronavirus, while nearly 34,500 have died from the disease, the national Department of Health and Social Care reports.