The relationship between Derval and her sailor fiance first blossomed four years ago as they flew home from the Beijing Olympics.
The couple, who are originally from Cork, share a home in south Dublin with their two dogs. They got engaged over the weekend.
Derval's mother, Eva O'Rourke, confirmed the good news but was keeping mum on any further details.
Eva said: "She did get engaged... But I wouldn't like to comment on it."
However the couple's home county of Cork is a likely wedding venue with Derval (31) hailing from Douglas and Peter (29) from Crosshaven.
At the closing ceremony of the Beijing Olympics in 2008, when both were nursing disappointments -- injury had denied Derval victory in the 100m hurdles, while Peter had finished 13th in his event -- they first struck up a conversation.
By happy circumstance, they found themselves sitting side by side on the long flight home to Ireland and spent hours in conversation. They were soon dating and later moved in together.
Derval has previously said that while they are both committed athletes, they rarely discuss life on the track or the waves when they are together.
"People would like to hear that we are sitting there analysing hurdle technique and discussing the possible weather conditions for Weymouth," she said.
The truth is "more boring", she added.
"He rings me, and tells me what positions they came. Otherwise I don't have a clue, just as he doesn't have a clue how to jump a hurdle. I'm not into sailing, and I don't even swim. But I understand the competitive side of it."