Johnson did not specify a date for the change. He noted that this will apply only to arrivals who have been "double vaccinated".
Transport Secretary Grant Shapps was due to update parliament with more details about the change later Monday.
The UK government only sets health policy for England, while devolved governments in Scotland, Wales and Northern Ireland administer their own rules.
Johnson earlier this month scrapped the need for arrivals in England to have pre-departure tests and quarantine until they have tested negative.
That had been mandated last month after Britain saw a fresh surge in cases due to the arrival of the Omicron variant in late November.
Announcing that easing of the rules, Johnson said the strain had now become so prevalent that enhanced testing measures for arrivals were having a "limited impact" on infections while imposing "significant costs on our travel industry".
The UK, among the worst hit countries in Europe by the pandemic with a virus death toll of nearly 154,000, has seen new cases fall dramatically from record daily levels late last month.
But some have criticised the relaxation of so many curbs so quickly, warning it could prompt a resurgence in cases and questioning whether Johnson has been making the changes for political reasons.
The embattled leader has been engulfed in scandals for weeks, leading to a clamour of calls for his resignation, including from within his own ruling Conservative party.
Many Tory lawmakers have grown increasingly weary of Covid-19 rules, with nearly 100 breaking ranks last month and rebelling against Johnson's beefing up of some restrictions before Christmas.