With current boss Louis van Gaal set to step down after the World Cup in Brazil later this year, Hiddink is due to take over for his second spell in charge of the national team for their UEFA Euro 2016 qualifying campaign.
And Hiddink, who has spent time in charge of Real Madrid and Chelsea, as well as Russia, Australia and South Korea, asked Van Nistelrooy to join him as assistant.
The former striker, who scored 35 goals in 70 appearances for his country, admits the offer came as a shock.
"It was a surprise call from Hiddink," he told UEFA.com. "I wasn't really expecting anything like that, but when a job like that comes by, it's an honour.
"Working with Hiddink, with his experience, for me, starting out as a coach, it's fantastic.
"Spending two years with him, with the Dutch national team, trying to help players improve - it can't get any better."
Van Nistelrooy's expertise as a player was mainly as a goal-poaching centre-forward, but he insists he can help players in all positions.
"I'll be an assistant coach, so I'll be helping everyone, together with Danny Blind (assistant coach)," he added.
"I can use my experiences - how to deal with pressure, how I prepared, how I did things, situations that occurred - but that's general things that I can share with any player."
