The pair exchanged vows in Westminster Cathedral on Saturday in front of a small group of close friends and family.
Initially, Downing Street would not comment on reports of the wedding but on Sunday morning a spokesman said: “The Prime Minister and Ms Symonds were married yesterday afternoon in a small ceremony at Westminster Cathedral.
“The couple will celebrate their wedding with family and friends next summer.”
They are said to have sent save-the-date cards to family and friends for the celebration on July 30, 2022.
It is understood Ms Symonds will take her husband’s surname and be known as Carrie Johnson.
A picture issued by No 10 of the couple in Downing Street’s garden after the wedding saw them gazing at each other.
Ms Symonds wore a £2,870 lace gown by Costarellos and a floral headband.
The Prime Minister wore a dark suit and blue tie, with a white flower in his buttonhole.
Another picture shared on Twitter by James Cleverly, the MP for Braintree, showed a less formal scene.
Ms Symonds is bare-foot cuddling up to her new husband. In the background, bales of hay can be seen. Glasses and jugs of cocktails balance on top. There also appears to be a colour stream of tassels and lanterns as decoration.
Reports suggest the small ceremony had been in the works for about six months.
The couple’s son, one-year-old Wilfred, attended the wedding, according to the Mail, as did two official witnesses.
Mr Johnson’s sibling’s Rachel, Jo and Leo are also understood to have attended, along with his father Stanley.
On Sunday morning, vaccines minister Nadhim Zahawi offered his congratulations to them but the wedding’s timing should not signal that lockdown easing will not happen on June 21.
Put to him that the timing suggested that a larger wedding after June 21 was not on the cards, Mr Zahawi told Sky News: “I wouldn’t extrapolate anything from that.”
He added: “On June 14, we will set out very clearly, the data that we are continuing to gather from step three, which was on May 17, and then we’ll share that with the nation, as the Prime Minister has done in each and every step from step one, two and three and then of course, step four.”
The couple announced their engagement – together with the news that they were expecting their first child – in February last year.
It is Mr Johnson’s third marriage, having finalised his divorce from his second wife Marina Wheeler in 2020.
He and Mrs Johnson have a son, Wilfred, who was born in April 2020.
The wedding ceremony at the Catholic cathedral was carried out by Father Daniel Humphreys, who had given the couple pre-marriage instructions, and baptised Wilfred last year, The Sun reported.
Shortly after 1.30pm, the cathedral was suddenly cleared of visitors, with staff saying it was going into lockdown, the newspaper said.
Half an hour later, a limousine carrying the bride swept into the piazza outside the main west door.
The ceremony meant Mr Johnson became the first prime minister to marry in office since Lord Liverpool married Mary Chester in 1822.
Weddings in England are currently subject to strict coronavirus restrictions.
Ceremonies are permitted for up to 30 people in Covid-secure venues.
Wedding receptions are also allowed for up to 30 people in a Covid-secure venue or outdoors.
But dancing is advised against due to the increased risk of transmission, except the couple’s traditional first dance.
Mr Johnson’s father Stanley was spotted in Downing Street after the ceremony, while guests and musicians were seen leaving No 10 on Saturday night.
The wedding comes at the end of a difficult week for the Prime Minister in which his former aide Dominic Cummings branded him unfit for office.
The Prime Minister’s former aide said Mrs Johnson had been desperate to oust him from his role as Mr Johnson’s right-hand man, and had sought to put her own friends in key positions.
Mr Cummings also claimed that in February 2020, when the pandemic was becoming a major global crisis, Mr Johnson was “distracted by finalising his divorce, his girlfriend wanted to announce being pregnant and an engagement, and his finances”.
Cabinet minister Therese Coffey sent her congratulations to the couple “on your marriage”.
Minister for children and families Vicky Ford sent her congratulations and “big love to Wilf”, adding: “So many weddings have been delayed and disrupted by covid. Life is always better with love,”
Northern Ireland’s First Minister Arlene Foster tweeted: “Huge congratulations to Boris Johnson & Carrie Symonds on your wedding.”
But Labour former frontbencher Jon Trickett said the wedding was “a good way to bury this week’s bad news” on Mr Cummings’ testimony, the spread of the Indian coronavirus variant and the row about funding of the Downing Street flat.
Fellow Labour MP Tonia Antoniazzi suggested the “emergency marriage plan” was an attempt to “deflect from negative press” from Mr Cummings.
She added: “They know he won’t be able to plan one in Chequers cos he won’t be PM next year…”