In May 2018, Russian pranksters managed to hold an 18-minute long phone call with Johnson by pretending to be Armenian Prime Minister Nikol Pashinyan. During the call, Johnson said the UK would continue to squeeze the Russian regime by targeting London-based oligarchs. The pranksters also brought up the Skripals' poisoning in Salisbury, though Johnson mostly struck to his public pronouncements.

In February 2018, Boris Johnson likened the challenges posed by the Irish border post-Brexit to the boundaries between different London boroughs. The Irish opposition described the comments as extraordinary, adding that "trivializing the very serious concerns relating to Ireland displays a dangerous ignorance that must be challenged."

During a foreign affairs committee hearing in November 2017, Johnson said British-Iranian citizen Nazanin Zaghari-Ratcliffe had been detained in Tehran while "simply teaching people journalism." Her family criticized the foreign secretary for making reportedly misleading comments that jeopardized her case. Iran has long viewed the BBC's Persian broadcasting service as a subversive arm of MI6.

Addressing a UK business forum in October 2017, Johnson told how fighting in Libya had prevented a group of investors from transforming the coastal city of Sirte "into the next Dubai." Johnson added that "the only thing they have got to do is clear the dead bodies away." Downing Street chided him for his remarks, while Johnson accused his critics of having "no knowledge or understanding" of Libya.

Johnson was accused of "incredible insensitivity" during a state visit to Myanmar in September 2017, as he recited part of a colonial-era Rudyard Kipling poem in front of local dignitaries at a sacred Buddhist site. Visibly embarrassed, Britain's Myanmar ambassador forced the foreign secretary to stop halfway through his impromptu recital.

Johnson caused uproar early on in his career as foreign secretary by comparing then French President Francois Hollande to a WWII prisoner of war guard for seeking to punish the UK for leaving the EU. “If Mr Hollande wants to administer punishment beatings to anybody who chooses to escape, rather in the manner of some World War II movie, I don’t think that is the way forward... ” said Johnson.

In May 2016, as the Brexit campaign was entering its ill-tempered final phase, Johnson told media that European history was marked by repeated attempts to unify the continent. "Napoleon, Hitler, various people tried this out, and it ends tragically," Johnson said. “The EU is an attempt to do this by different methods. But fundamentally ... there is no underlying loyalty to the idea of Europe.”

US President Barack Obama's intervention in the Brexit referendum in April 2016 provoked a furious reaction from Johnson. After Obama said the UK would be better off remaining part of the EU, Johnson described the US president "part Kenyan" and accused him of harboring an "ancestral dislike" of the United Kingdom.

After Turkey's Recep Tayyip Erdogan complained about German comedian Jan Böhmermann calling him a "goat f---er" in March 2016, the UK's "Spectator" newspaper, which Johnson used to edit, ran a competition for readers to submit their own poems about Erdogan. Johnson's poem, in which he called the Turkish president from Ankara "a terrific wankerer," was awarded the £1,000 ($1,325, €1,127) prize.

In October 2015, Boris Johnson was forced to apologize as his competitive nature on the sports field saw him knock over a 10-year-old during what was supposed to be an informal game of rugby in Tokyo. Despite being bulldozed to the ground by the then-mayor of London, the young Toki Sekiguchi appeared unfazed by the incident, saying later he "enjoyed" meeting Johnson.

Johnson sought to mark Team GB's first gold medal at the 2012 Olympic Games in London with a high flying zip-line act. However, as he zipped across Victoria Park, the mayor lost momentum and came to a halt, leaving him dangling above a crowd of mystified onlookers. “I think they needed to test this on somebody going a bit faster,” he told onlookers, before urging them to get him a ladder.

Johnson was lampooned for one of his columns in "The Telegraph" in 2006, in which he compared infighting within the UK's Conservative and Labour parties to "Papua New Guinea-style orgies of cannibalism and chief-killing." Johnson issued an openly sarcastic apology, saying he did not mean to insult the people of Papua New Guinea, "who I am sure lead lives of blameless bourgeois domesticity."

As editor of the "Spectator" in 2004, Johnson claimed that drunken supporters of Liverpool football club were partly to blame for the 1989 Hillsborough disaster, in which 96 fans lost their lives. Johnson went on to accuse Liverpudlians of wallowing in their "victims' status." A coroner's inquest concluded in 2016 that the supporters were unlawfully killed due to police negligence.

In another column for the "Daily Telegraph" in 2002, Johnson wrote that the Queen loved the Commonwealth "partly because it supplies her with regular cheering crowds of flag-waving piccaninnies." Also writing ahead of Prime Minister Tony Blair's trip to the Democratic Republic of Congo, the UK's future top diplomat described how "the tribal warriors will all break out in watermelon smiles."