The show has sparked controversy for fictionalising events during its hugely popular fourth series.
But royal commentator, Richard Fitzwilliams, fears producers could leave the royals feeling "hurt" if they cover the 1997 crash.
And he urged them to ensure the seismic event is accurately portrayed if they decide to feature it.
Fitzwilliams told Daily Star: "There is no doubt that personally – and I don't know whether it will be next series or the last series – I think it will be very hurtful.
"I don't know the context in which this is going to be handled, but I can only say I don't have any confidence given what we have just seen in the fourth."
He added: "For anything as sensitive as that, naturally, the whole point is that we know what happened.
"Chased by paparazzi who were lower than vermin, a drink-driver crashed the Mercedes and they weren't wearing seat belts, tragically.
"The whole point is that there are the recognised facts as to what happened and, if it is covered as I anticipate it would be, one would expect The Crown to stick to what I would call recognised facts."
The Princess of Wales was being driven at high speed in Paris before her vehicle smashed into a tunnel pillar.
An inquest later determined she and Dodi Fayed were unlawfully killed by the "gross negligence" of driver Henri Paul and the paparazzi who were following him.
Paul, who also died in the crash, was drink-driving. Seat belts were not used, the inquest found.
The death marked one of the most significant events in British royal history, and Diana left behind sons Prince William and Prince Harry along with husband Prince Charles.
For the first time, Diana has been featured in The Crown in season four.
But there are fears the show is being received as reality.
Culture secretary, Oliver Dowden, said of the show: "It's a beautifully produced work of fiction, so as with other TV productions, Netflix should be very clear at the beginning it is just that.
"Without this, I fear a generation of viewers who did not live through these events may mistake fiction for fact."
And Fitzwilliams agrees, adding: "One dreads to think how they will cover the annus horribilis."
He continued: "You have a huge audience and many will believe it's fact."
Daily Star has approached the producers of The Crown for a response.