Gustavo Alfaro's men came through the notoriously-difficult South American qualifying section to book their place in Qatar, although complaints from their rivals over an ineligible player used during that qualification campaign meant that their place at the tournament was not rubber-stamped until as recently as this month.
La Tri will go into the opening game as favourites given Qatar's lowly ranking and lack of experience on the biggest stage, although with Senegal and Netherlands also in Group A they will know it is imperative to get off to a winning start.
Here, Sports Mole looks at some reasons why Ecuador should be confident of kicking off their campaign with three points.
World Cup experience
Ecuador did not qualify for the 2018 World Cup, but Qatar will be their fourth taste of the finals since first qualifying in 2002.
Crucially in the experience stakes, Qatar have never played a single World Cup match, whereas Ecuador have played 10, winning four of those, drawing once and losing five times.
Sunday's match will be the first time they have faced a non-European nation in their opening game of the tournament, while their only victory in their curtain-raiser came against Poland in 2006.
That helped them reach the last 16 for the first and so far only time, so they know that getting off to a good start bodes well for further progress in the competition - especially this year, with Netherlands and Senegal to come in their other two group games.
Whereas they do have that World Cup experience to fall back on, Alfaro has brought a relatively inexperienced squad to Qatar, with their 26-man selection containing 628 caps compared to 1,472 in the Qatari camp.
Ecuador's starting lineups in World Cup qualifying also had the youngest average age of any team, which could be seen as a positive or a negative on the World Cup stage.
History
Aside from Ecuador's superior World Cup experience, there is also the weight of history on the shoulders of Qatar as they look to do themselves justice on the pitch as hosts.
While home teams have generally fared well at World Cups down the years - South Africa in 2010 aside - teams from the AFC confederation do not have such a storied history on their debuts at the competition.
Indeed, of the 11 previous such teams to have played their first World Cup game, not a single one of them have won it, with 10 defeats and just one draw.
Kuwait are the only previous nation from the AFC confederation to avoid defeat in their first World Cup outing, securing a 1-1 draw with Czechoslovakia back in 1982.
In contrast, though, no host nation has ever lost when playing the opening game of a World Cup, so history could go one of two ways on Sunday.
Goal threats
With only three outfield players over the age of 30 and only two players in the squad with more than 50 caps to their names, at first glance the goalscoring exploits of this Ecuador squad do not look particularly impressive.
Indeed, they only have 74 international goals throughout the squad compared to 192 in the Qatari ranks, and almost half of that 74-goal tally comes from Enner Valencia, Ecuador's leading scorer of all time with 35.
However, they had no problem finding the back of the net during qualifying for the World Cup, posting their highest-ever goalscoring tally during qualification with 27.
In Valencia they have a proven goalscorer on the international stage, while it is also worth keeping an eye out for Brighton & Hove Albion's Pervis Estupinan putting the ball on a plate for his strikers.
The left-back created 22 chances for his teammates during the qualification campaign, which was more than any other defender in a CONMEBOL section which includes the two tournament front-runners Brazil and Argentina.
Extra motivation
There may be a part of the Ecuador squad that are simply happy to have made it to the World Cup, with their place at the tournament appearing under threat until as recently as two weeks ago.
Chile and Peru both lodged complaints against the nation after the Colombian-born Byron Castillo featured in eight of their qualifying games, having used false information about his place of birth to secure an Ecuadorian passport.
The Court of Arbitration for Sport ultimately ruled that Castillo was eligible and that Ecuador could keep their World Cup place, but they will begin the next qualifying section with a three-point deduction, which in such a competitive campaign could be the difference between making it to the 2026 World Cup or not.
There should be even more motivation amongst the Ecuadorian squad to make the most of this opportunity, then, with the odds already stacked against them returning to this stage in four years' time.
There may also be an element of the pressure being off given they could have been kicked out of the tournament anyway, and they will no doubt be looking to take full advantage of the reprieve.