The producer of the SABC show, Samantha Moon, told the BBC the decision was taken after consulting the family.
Tropika Island of Treasure was broadcast on Saturday evening.
Meanwhile, Mr Pistorius's uncle said on Saturday that the athlete was "numb with shock, as well as grief".'Vibrant and funny'
Tropika Island of Treasure was made on location in Jamaica, with several personalities competing for a one million rand ($113,500) prize.
As a family we are trying to be strong and supportive to Oscar as any close family would be in these dreadful circumstances”Arnold Pistorius,Uncle
At the start of the programme, Ms Steenkamp, 29, was seen talking about her appearance on it, shortly before she left Jamaica to return home: "The way that you go out and make your exit is so important. You have either made an impact in a positive way or a negative way."
Ms Moon said the decision to air the programme had nothing to do with ratings.
She told the BBC's Newshour: "I took it after consultation with her family and the feeling was that this is an amazing woman who you don't have very much in the public domain except for the work she was most well known for... which is her modelling work.
"We felt that it was important for people to know that there was more to the narrative of Reeva than an exceptionally beautiful girl in a bikini, that she was strong and vibrant and funny and lovely and that this is a tragedy on an unspeakable level."
Reeva's cousin, Sharon Steenkamp, told the Associated Press news agency the family did not oppose the airing, saying: "Her last words to us personally was that she wants us to watch it."
Oscar Pistorius appeared in court on Friday charged with murderHowever, one South African TV critic, Thinus Ferreira, said the motives were questionable and "very much about the commercial considerations".
He said that if the show had been pulled it would have upset sponsors, advertising and scheduling.
The audience was expected to be far higher than the 2.5 million to 3 million who usually watch the show, now in its fifth season.
Meanwhile, Oscar Pistorius's uncle, Arnold, said the Olympic and Paralympic star was "numb with shock, as well as grief" after Ms Steenkamp's death.
He repeated the family's opposition to the prosecution's pursuit of a "premeditated murder" charge.
Arnold Pistorius said Ms Steenkamp was someone the family had "got to know well and care for deeply over the last few months".
He added: "They had plans together and Oscar was happier in his private life than he had been for a long time.
Standing with Oscar's sister Aimee, Arnold Pistorius, Oscar's uncle, says the athlete is "numb with shock"
"We are all grieving for Reeva, her family and her friends," he said.
"We, as a family, are also battling to come to terms with Oscar being charged with murder. Words cannot adequately describe our feelings.
"The lives of our entire family have been turned upside down forever by this unimaginable human tragedy and Reeva's family have suffered a terrible loss.
"As a family we are trying to be strong and supportive to Oscar as any close family would be in these dreadful circumstances."
Mr Pistorius is in police custody ahead of a bail hearing on Tuesday.
Ms Steenkamp, a model and law graduate, was shot dead inside the Pretoria home of Mr Pistorius in the early hours of Thursday morning.
The pair had been together since November.
A memorial service for Reeva Steenkamp will be held in Port Elizabeth on Tuesday, SABC has reported.
