Anti-war campaigners call on Trump to avoid military action against North Korea.
The protests come as Trump has ratcheted up tensions with North Korea by threatening it with military action.
Protesters from Stop the War campaign gathered outside the embassy on Grosvenor Square on Friday.
They called on Trump to pursue a diplomatic solution for North Korea’s nuclear and missile programs.
A man wearing a Trump mask was seen among the protesters, who took to the streets, fearing a military confrontation between Washington and Pyongyang could be inevitable.
Tensions have mounted over North Korea’s nuclear and missile programs with the two countries recently trading serious threats of an invasion.
Trump threatened earlier this week to unleash “fire and fury like the world has never seen” on the North.
In response to the threat, North Korea said a plan to fire four missiles at an area near the US Pacific territory of Guam would be ready in days. The tiny island is home to major US air and naval facilities.
On Thursday, Trump said warning North Korea with “fire and fury” may not have been “tough enough,” and that the US is “backed by 100 percent by our military, we are backed by everybody and we are backed by many other leaders.”
The president went further on Friday morning, when he took to twitter writing that US military options were “locked and loaded” for use if Pyongyang “acted unwisely.”
The US has long been opposed to the North Korean missile and military nuclear programs.
Pyongyang, which conducted two successful tests of an intercontinental ballistic missile last month, says it needs the weapons to defend itself against the threat of an invasion by its adversaries.