The Hollywood actor's phone wouldn't stop ringing following Houston's February (12) death as media outlets from all over the world reached out to hear his thoughts on the tragic superstar's passing.
The Dances with Wolves star shunned all requests because he didn't feel the time or the "forum" was right to open up about his close friendship with the I Will Always Love You hitmaker - and it wasn't until he was contacted by Warwick herself that he finally agreed to speak out.
But Costner insists he only chose to speak at Houston's New Jersey funeral as a favour to Warwick to show his support for the grieving family.
He explains, "I had consistently turned down doing sound bytes and going on news programmes to talk about Whitney. And the pressure began to build on some level about, 'Well, when are you going to say something, are you going to say something?'
"Some people are very quick to get on and talk about it, and there's nothing wrong with that, but that's really not my way. And I actually didn't realise that it seemed that a lot of people did want to hear from me on some level. Sometimes you don't understand, and somebody has to say, 'People really do want to hear it.'
"And I was thinking, 'Oh my goodness,' and I still didn't think any of the forums that I was seeing (like talk shows) were right, to be honest. There was one notion that maybe I would go on the Image Awards and present a film clip, which would be one or two lines and here's the clip, and she meant a lot more to me than that.
"When I got a call from Dionne Warwick, that's when I said I would come. And I'm not saying that was the right forum. It was one where I chose to support Dionne at that moment."