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The 21-year-old Welshman failed to match Serik Sapiyev's work-rate at the ExCel Arena on Sunday and lost 9-17 in the welterweight final.
Evans' silver brought the number of Olympic medals won by Welsh competitors at London 2012 to seven, their highest total from any Games.
Jade Jones, Tom James and Geraint Thomas were the three gold medallists.
Evans joined Chris Bartley and Hannah Mills in winning silver, while Sarah Thomas added a bronze to the Welsh haul.
Evans's success gave Wales its best boxing medal in the history of the games, trumping Ralph Evans's bronze in 1972 Munich Games.
His hard road to the London 2012 final, which also included an enthralling single point semi-final win over Ukraine's world champion and world number one Taras Shelestyuk, caught up with him as Sapiyev pulled away to win.
"I've had four hard fights and I've got no excuses. He was sharper on the day and I didn't stick to my plan quite as I should have," Evans said.
"I beat the Ukrainian world champion, the number one in the world. Obviously I'm still young, I'm only 21 - I'm one of the youngest seniors here - so I've done well and I'm over the moon with getting to the final."
Evans's fellow martial artist Jones in the taekwondo,coxless four rower James and team pursuit cyclist Thomas led the way for the Welsh contingent at London 2012 by winning gold medals as part of a great British performance that claimed 29 golds in a 65-medal haul.
Lightweight four rower Bartley and 470 class sailor Mills have claimed silvers at London 2012, with hockey player Thomas winning bronze.
Welsh athletes had claimed five medals at three previous Olympics - at Stockholm 1912, London 1948 and at Beijing four years ago - so a total of seven Olympic medals at these Games represents a stand-out achievement.
The haul was reached despite two of the top tips for gold, 400m hurdler Dai Greene and triathlete Helen Jenkins, not fulfilling expectations after their preparations were disrupted by injury.
Green also finished just outside the medals as part of the GB 4x400m relay team that came fourth in the final, while sprinter Christian Malcolm's last hopes were dashed when the 4x100m relay team was disqualified in the heats.
The only milestone missed was equalling the mark of four gold medals won at a single Games set at Antwerp 1920.
Ninety-two years ago it was water polo players Paulo Radmilovic and Christopher Jones, along with 4x400m relay runners Cecil Griffiths and John Ainsworth-Davies who spearheaded the Welsh effort under the banner of Great Britain.
Wales also contributed a record 30 competitors to the GB squad, boosted by the five footballers selected for the men's team that lost on penalties to South Korea in the quarter-finals.
Boxer Fred Evans had to settle for a silver medal as a record-breaking Olympics for Welsh competitors ended.