He completed the 702-mile trek at the South Pole on Christmas Day, 12 days earlier than planned.
Lt Sears carried out the trek for charity.
Antarctic Ghurka wrote on its Facebook page that the trek was "an effort to raise £25,000 for the Gurkha Welfare Trust".
It added: "The 1100km journey from Hercules Inlet to the South Pole is the equivalent of walking from London to the Czech Republic...it's just a bit colder...and windier...and there are crevasses to fall into...and you have to drag all your food and shelter with you...but otherwise it's basically the same."
The BBC reports that the first part of the journey from Hercules Inlet, where sea ice meets land in Antarctica, is considered the most dangerous part, as the ground is riddled with crevasses.
Lt sears was not roped to a teammate who could help stop him from falling, and used skis to cross the ice.
The 6ft 5in soldier pulled a sledge containing all of his food, fuel and equipment that, at more than 100kg (220lb), was heavier than him.
He said at points he hit a wall, and on Christmas Eve felt like he couldn't take another step, but persevered.
Speaking to the Telegraph, he said: "It's been an amazing 5 weeks, very tough at times but it all feels worth it now.
"I've been alone in a tent for nearly six weeks so it's all a bit overwhelming
"I can't wait to have a shower and get some food in me. I've been dreaming about it since day 3!".
He admitted that his mum had not initially been keen on the idea, but was very supportive.
He said: "She is eternally suffering because of me, I thought I managed to annoy her the most I possibly could when I joined the infantry and then I chuck this on her as well.
"I don't think she's slept for 38 days and she is as tired as I am."
Andy's mum Judy congratulated Sears on Twitter.
Well done Scott Sears - (brother of Andys wife Kim) youngest person to reach the South Pole on a solo mission. Got there on Christmas Day......🌟 https://t.co/UG4VF2DTDv
Lt Sears hopes to make it back to London in time for New Year's celebrations.
Celebrity Christmas and New Year holiday destinations
Celebrity Christmas and New Year holiday destinations
Celebs love Barbados for a winter escape and the likes of Simon Cowell, Sir Philip Green and Rihanna celebrate New Year's Eve on the Caribbean island. Simon likes to stay at posh Sandy Lane, where he has been pictured jet-skiing, strolling the white sands with girlfriend Lauren Silverman and browsing art from local beach vendors. Rihanna returns to Barbados, where she was born, to spend Christmas with her family.
The parties, fireworks, beaches - Sydney is one of the hottest celebrity destinations to ring in the New Year, where the likes of Rebel Wilson, Alessandra Ambrosia and Sam Smith have celebrated this time of year in the sunshine. Sam was last year pictured climbing the Harbour Bridge before the New Year countdown, while Kelly Brook took to Bondi Beach to party.
Kate Hudson, Mariah Carey and Antonio Banderas have all spent Christmas on the ski slopes at Aspen, opting for the snowy resort for a festive break with their families. The resort's celebrity pack are often spotted shopping, dining and skiing in the winter wonderland, as well as strutting through the town wearing fur and high heels.
Kate Moss appears to have fallen in love with Brazil and is reportedly returning to Rio de Janeiro with friends to celebrate the New Year for the second year in a row. While there, Kate can party with over two million other revellers as the city hosts one of the largest NYE celebrations in the world. According to The Sun, the supermodel will be jetting off to Rio with her new boyfriend Nicolas von Bismark's mother and has invited Fran Cutler, Sadie Frost and the Primrose Hill set to join her. Last year, Naomi Campbell and Victoria's Secret model Alessandra Ambrosio also spent New Year's Eve in Brazil.
While St Barths is the Caribbean island where the stars like to be seen at Christmas, neighbouring isle Anguilla is perfect for those who like to escape the paps on an exotic festive break. Paul McCartney, Beyoncé and Jay-Z have spent Christmas on this hidden gem, with the Viceroy Anguilla and Malliouhana popular hotels among the celebs. Home to some of the Caribbean's best beaches and superb dining, we can see why the A-listers choose to escape to Anguilla for Christmas.
For glitz, glamour and fun in the sun, the stars head for Dubai to celebrate Christmas and New Year in style. Gigi Hadid and Selena Gomez were pictured sitting on the beach outside the Jumeirah Beach Hotel in their New Year's dresses, where they were joined by fashion designer Olivier Rousteing and Kendall Jenner. The group partied on the hotel's private beach as they watched the fireworks overhead. Book a stay in the Beit al Bahar villas, where celebrities often choose to stay, from £1,650 per person for seven nights including flights with luxtripper.co.uk. The villas come with an 18-carat gold plated bathroom with a sunken circular bath and the exclusivity of a private, shaded pergola.
Movie stars Ben Affleck and Jennifer Garner are allegedly spending Christmas in the rolling mountains of Montana with their young children to escape the prying eyes of the media following their split earlier this year. According to US Weekly, the family will stay at the exclusive Yellowstone Club in Big Sky. You can follow in their footsteps and enjoy a celeb-inspired trip to Montana by staying at DoubleTree by Hilton Hotel Missoula - Edgewater, located on the banks of the Clark Fork River in the heart of the Northern Rockies and just minutes from beautiful countryside, snowy mountains and world-class fly fishing, from £59 per night.