Head coach Fernando Santos' side will provide arguably the toughest test for the Euro novices at AS Saint-Étienne's Stade Geoffroy-Guichard.
Portugal lacking offensive threat
Despite having one of the best goal-scorers of the past decade in Cristiano Ronaldo, Portugal struggled to find the back of the net throughout their qualifying campaign. All of their wins in qualifying came via a one-goal deficit, with five of the seven scorelines being 1-0 victories. Out of the 11 goals in their qualifying campaign, Real Madrid's Ronaldo contributed five - 45 per cent of their tally.
However, with the average age of Iceland's defence at 31, A Selecção will be looking to expose the ageing back four with the pace and skill of both Ronaldo and Nani, with Ricardo Quaresma a doubt ahead of the fixture. Despite it coming against 93rd ranked Estonia, Portugal have shown signs of the attacking threat they can possess, as they came out dominant in a ruthless 7-0 thumping.
If they are to capatilise on the quality they posses over Iceland, midfield maestro João Moutinho will be significant. Linking the play from the defence to attack will be key from Moutinho if Portugal are to utilise Ronaldo effectively.
Can Iceland make a statement?
Depending on the outcome of the earlier group game - Austria - Hungary - a win for Iceland could set a bold statement to the rest of the group. Defeating strong favourites to win the whole competition would not only put Austria and Hungary on notice, but it'd also prove that their impressive qualifying campaign was no fluke.
Swansea City midfielder Gylfi Sigurðsson will be the focal point of Iceland's offence. After scoring 11 goals in 33 games in the past Premier League season, he will now have the opportunity to prove that he can do it on the big stage.
For such a small nation, he is pleasantly not the only widely recognised big name amongst the Iceland squad. Ex-Chelsea and FC Barcelona forward Eiður Guðjohnsen is set to make his first, and most likely only, appearance at a major international tournament due to his career coming near to an end at the age of 37.
Although he has only scored twice internationally in the last six years, his experience playing against the world's biggest names will prove valuable to many of the more inexperienced names within the squad.
As previously mentioned, Quaresma is the only injury doubt amongst the Portugal squad. Nani is the most favourable pick to replace him if Santos decides to rest Quaresma.
Whereas Iceland have three doubts heading into tomorrow's fixture in Sigurðsson, Kolbeinn Sigthorsson and Aron Gunnarsson. However, since the tournament has begun, they have all be reported to be fit for selection, leaving joint managers Lars Lagerbäck and Heimir Hallgrímsson with a full squad to choose from.