Attacker Rafa has come to prominence in the Primeira Liga with three goals in 19 appearances for a Braga side challenging for a spot in the UEFA Europa League.
Cavaleiro's selection in the team comes as something of a surprise considering his lack of experience since breaking into Benfica's first team this season.
But the 20-year-old can play on either wing or in a more central position up front and his versatility could count in his favour when coach Paulo Bento considers his squad.
Explaining the decision to include the pair, Bento said: "We have tracked their progress at their clubs and in the Portugal youth levels and we decided this was the right time to call them up.
"(Rafa) can play on the flanks and also as a number 10, which gives us several solutions.
"Ivan has played a lot for Benfica B. The fact he can play on either flank or as a centre-forward gives the squad more solutions."
Regular number one goalkeeper Rui Patricio is not included in the squad as Bento wants to take a closer look at understudy Anthony Lopes, while Manchester winger Nani is absent with a hamstring injury.
The likes of striker Edinho and defensive duo Miguel Lopes and Rolando also return to the fold, while Bruno Alves and Helder Postiga are notable omissions.
But Bento insists there is nothing to read in terms of inclusions and exclusions, adding: "The fact certain players are in this squad does not mean they will be in the World Cup squad.
"Likewise, the fact certain players have not been called up on this occasion does not mean that they cannot be selected on 19 May."
Portugal required a play-off victory over Sweden (a 4-2 aggregate triumph) to secure their spot at the 2014 FIFA World Cup, as did opponents Cameroon, who defeated Tunisia 4-1 on aggregate.
Coach Volker Finke has recalled 33-year-old Kaiserslautern forward Mohammadou Idrissou after he was not selected for the second leg with Tunisia.
Idrissou is likely to replace the injured Pierre Achille Webo, while Sevilla midfielder Stephane Mbia (knee) is unavailable.
Finke - like Bento - will also take the opportunity to run the rule over his squad with the World Cup on the horizon, with 18-year-old Barcelona B centre-back Frank Bagnack handed his first call-up to the national team.
Speaking about his squad, Finke told camfoot.com: "I always try to mix the young and old.
"I think it is also good for the future, because you need the experience."
The two sides last met in June 2010, when Portugal triumphed 3-1.
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