Armstrong, the Scotland under-21 captain, is thrilled to see his Dundee United team-mate get the call-up from Gordon Strachan for tomorrow night's friendly with Poland, after impressing in his first season in the SPFL Premiership since signing from Queen's Park last summer.
Armstrong, who is preparing for his own taste of international action in Wednesday night's friendly with Hungary at Tannadice, is convinced 19-year-old Robertson will take his first cap in his stride should Strachan decide to call upon the full-back.
"I think if Andy is given the chance, he will do well in that environment," Armstrong said. "Playing on the international stage will not faze him as that is the sort of boy he is. It is thoroughly deserved and earned and I hope he enjoys it.
"Andy has performed exceptionally well since he came to Tannadice. He doesn't get too carried away with himself. He trains the way he plays and that never differs. There was a bit of good natured banter when he got the call but everyone at the club is just really happy for him.
"He has made the position his own at United and I don't see why he can't do the same with Scotland. His call-up shows there is a great incentive there for younger boys like myself to make the step up.
"You know the chance is available if you put the performances in."
Armstrong will wear the captain's armband against their Hungarian visitors in their final warm-up game before facing the Netherlands in May as they bid to keep alive their hopes of reaching the European Championships in the Czech Republic in 2015.
"I never really saw myself as a captain per se so I was quite surprised to be asked to be honest," Armstrong admitted. "Billy [Stark, the under-21 coach] asked me when we went over to Marbella to play a few games in a little tournament. Myself and Ryan Jack captained the side.
"Jacko got injured and it fell to me and I have remained skipper since. I am not too loud or shout a lot like some other captains do.
"Looking back when I first came in to the under-21s, there were a lot of older players who had played at that level before. Now I feel quite old in comparison to some of the boys who are here. But it is nice to be able to help the younger boys come through.
"Usually the under-21s play at St Mirren which is a nice park but it is good to be up here and close to home, playing at a ground I am familiar with. It is always an honour to lead the team out, especially for your country. I have had the privilege of doing it a couple of times at home for the club and every time it's special."
Scotland sit fourth in qualifying Group Three and face an uphill battle to make the finals, although Armstrong is refusing to give up hope. "I definitely wouldn't say it was over," he said. "We have maybe put a wee bit more pressure on ourselves to pull off results but we remain optimistic. We will just take each game as it comes starting with Wednesday night. It is an important match and we will be looking for a good performance to take into the main match against Holland in May.
"It is a relatively new squad so it is a great chance for us all to get to know one another."