Maj Matthew Collins, 38, from Backwell, in Somerset, and L/Sgt Mark Burgan, 28, from Liverpool, died on Wednesday when their vehicle hit a roadside bomb.
Their commanding officer said their loss was "a devastating blow".
Their deaths take to 362 the total number of UK military personnel to have died in Afghanistan since 2001.
Maj Collins joined 1st Battalion Irish Guards and had also served in Kosovo, Sierra Leone, Northern Ireland and Iraq.
He was the company commander of Number 3 Company, and leaves behind two children and his wife, Lucy.
His family said in a statement: "Not only a soldier but a caring husband, devoted father to Freya and Charlie, caring son, wonderful brother and friend to many. We will all miss him and remember him always."
L/Sgt Mark Burgan joined the Guards in 1999 and had also served in Northern Ireland and Iraq.
His wife, Leanne, said: "I am so honoured to be Mark's wife. I will always love my hero.
"Mark was an extremely proud Irish Guardsman, dad, husband, brother and son. He will forever be in our hearts."
The two men were returning to base from an operation aimed at disrupting insurgent groups in the Nahr-e Saraj district of Helmand province when their vehicle hit a roadside bomb.
Lt Col Christopher Ghika, commanding officer of 1st Battalion Irish Guards, said: "Two more committed and professional soldiers it would be hard to meet; they epitomised what it meant to be a member of this family regiment."
He said Maj Collins had played a key role in training Afghan soldiers, adding: "It is a telling fact that there is a deep sense of sorrow hanging over the 3rd Kandak of the Afghan Brigade today, such is the respect in which they held Matt Collins."
Speaking about L/Sgt Burgan, Lt Col Ghika said: "The notes given to me by his company commander, alongside whom he died, say it all: 'Knows what has to be done, does it brilliantly and has the next thing ready before you ask'."
The commanding officer added: "It is perhaps a comment on the character of this regiment that both Lucy Collins and Leanne Burgan are the daughters of distinguished and long serving Irish Guardsmen.
"The events of last night are a family tragedy in every sense."
Defence Secretary Liam Fox said both were men "of great experience and exemplary commitment".
"They have laid down their lives protecting our national security, a loss made all the more poignant as they were so close to finishing their tour of duty and returning home," he said.

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The 21-year-old English swimmer was joined on the podium by Scotland's Ross Murdoch, 22, who claimed silver.
Peaty, Chris Walker-Hebborn, Siobhan-Marie O'Connor and Fran Halsall then won mixed 4x100m medley relay gold.
Halsall, 26, also took a bronze medal in women's 50m butterfly final, with 21-year-old Ben Proud finishing third in the men's event.
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"There was amazing support in the venue tonight and it's definitely one of the best races I've had," said Peaty.
"And to have Ross alongside me is just great."
The reigning world and European champion set a new championship record of 58.36secs in his final and added: "That puts me in a great place going into Rio."
Two soldiers from 1st Battalion Irish Guards killed in Afghanistan just six days before they were due to return home have been named.
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Great Britain's Adam Peaty won gold in the men's 100m breaststroke final at the European Championships in London.