About 600 commandos, based at Bickleigh Barracks, paraded through Plymouth city centre earlier, led by a military band and cheered on by a large crowd.
42 Commando spent six months in Afghanistan's Helmand Province, during which time three men died in combat.
They were in Afghanistan as part of 3 Commando Brigade.
Another mother who had travelled from London commented: "I'm very proud of them, they are amazing and so young.
"You may be dead against the war, as I was, but you have to admire them."
Capt Lawrence Clinton, who had been cheered-on by his three children and nephews and nieces said: "It was great. We got an enormous sense of pride and satisfaction from seeing the crowd.
"I just can't believe how many people were there. It was wonderful, thank you Plymouth."
42 Commando Commander, Lt Col Charlie Stickland, told BBC News: "Today has been extraordinary, we had no idea the reception Plymouth was going to give us.
"The smiley boys of 42 Commando were certainly smiling today. It was brilliant."