Paris - Gare du Nord - Europcar rental office

It's at 18, rue de Dunkerque.

Between the Monop' Daily and Starbucks.

Thank you!

Is there a safety issue walking between them at 9pm on a weekday? I could take Metro as an alternative, but a 10 min walk seems like a good idea after a long train ride.

There is no safety issue at all - if you stick to the sidewalk!
Despite what you might have heard or read, the area has been cleaned up and is not seedy or gritty at all.

Nadine, rue de Dunkerque is the road that runs along the front face of the station. 18, rue de Dunkerque is showing up as the station facia. The website implies it is in the station:

Adresse: Gare Sncf Lev-1 18 Rue De Dunkerque,

No 10 minute walk involved.

Make sure you know when the office is closed.
You can enter Europcar in 18 rue de Dunkerque or inside the station.

Thank you all for your comments.

I should have been a little more specific. But, in my attempt to trim down my question, I caused confusion. I'm arriving at Gare de l'Est at 8:40pm (after the Europcar office at Gare de l'Est closes at 6:30pm), so I have 10 min walk from Gare de l'Est to Gare du Nord where the Europcar office is open later.

I read about the seedy state around Gare du Nord and was concerned about the walk. I can take Metro, but it seems a waste and probably includes stairs as well as 10 min of walking. just not on the city streets.

Nadine

Nadine, Gare de l'Est to Gare du Nord is an easy 10 minute. It is probably as quick if not quicker to walk than do the one stop on the métro, by the time you have added the the many stairs down into the bowels of the métro system and back up again, plus having to buy a ticket.
Lots of people do it, you will see others walking both ways.
Here is a map/photo: http://www.nouvelle-liaison-gare-nord-est.fr/hypercarte_v6.html
You go along the side of the Gare de l'Est (Rue d'Alsace), then turn left into the Rue de Dunkerque. The only catch is a set of stairs along the side of the station (where it says "Les ascenseurs au sud de la rue d'Alsace"). You will have to carry your case up. Avoiding the stairs involves a longer route.
When you come out the side entrance of Gare de l'Est, this is what you see: https://www.google.ch/maps/@48.8774493,2.3582139,2a,75y,23.59h,84.33t/data=!3m7!1e1!3m5!1sNipNnPuroUK-JVKl0Rq2zw!2e0!6s%2F%2Fgeo2.ggpht.com%2Fcbk%3Fpanoid%3DNipNnPuroUK-JVKl0Rq2zw%26output%3Dthumbnail%26cb_client%3Dmaps_sv.tactile.gps%26thumb%3D2%26w%3D203%26h%3D100%26yaw%3D306.75085%26pitch%3D0%26thumbfov%3D100!7i13312!8i6656?dcr=0

I don't know where this reputation for "seedy" comes from, it has never struck me that way, just busy.

Thank you so much for your help.

Nadine