A family of three, including a small child, are the first people to arrive in the UK under the government's "one in, one out" agreement with France.
The move follows the removal of the four migrants being deported from the UK so far under the pilot scheme.
"This is a clear message to people-smuggling gangs that illegal entry into the UK will not be tolerated," a Home Office spokesperson said.
"We will continue to detain and remove those who arrive by small boat."
The "one in, one out" scheme was announced by Prime Minister Sir Keir Starmer and French President Emmanuel Macron in July.
Under the treaty, France agreed to take back migrants who had travelled to the UK by small boat and had their asylum claim withdrawn or declared inadmissible.
For each person returned to France, the UK will accept someone with a case for protection as a refugee who has not attempted to cross the Channel.
Last week, an Indian national was the first person to be removed from the UK, followed days later by another Eritrean man, despite a legal bid to delay his departure.
Last Friday, Home Office sources said an Iranian male had also been returned to France, and on Monday the department said an Afghan person had been returned earlier that day.
More than 30,000 people have crossed the Channel in small boats so far this year.
The total number of small boat crossings in the English Channel this year has dipped below record levels for the first time since 3 March, new government figures suggest.
In the year to 23 September, 32,188 people arrived in the UK by small boat, 148 fewer than at the same point in 2022.
Despite crossings falling slightly below 2022 levels so far this year, 2025 has still seen more crossings than most previous years, particularly in spring and summer.
French authorities say they have prevented more than 17,600 attempted crossings this year. But under maritime law, French officers say they cannot intervene once boats are in the water unless there is a threat to life.