How to get from Gare du Nord to Gare St. Lazare

The RER requires about 12 minutes of walking. Bus 43 which connect both stations requires about 5 minutes of walking. I think the bus is easier but I could be biased.

Or a taxi if you have much luggage. It'll cost more and might take longer than RER, but faster than bus and certainly "easier" than anything else.

Thanks for the replies! How about Uber - any thoughts?

Bus 26 is good too.

Uber is not a great idea for this transfer. There is a taxi stand on the west side of the station. In the time it will take you to contact Uber and figure out where your driver will be (and it darn sure will not be the official taxi line because Ubers cannot use it), you could easily be in a taxi and on your way.

Thanks for all the responses - I guess we'll do the bus - sounds like the best option.

Download the Paris Metro app and I have another called Next Stop Paris. I have been using them at home to get familiar with routes. I have one tour I need to meet for 7:45am, and was able to easily figure it out. Google Maps isn’t bad either if you set it to train mode.

Four of us did that trip in mid-June. We all had luggage and we used a cab. Then a little under an hour in another train and a cab from Vernon to Giverny and we were getting settled in. Our innkeeper called the bakery and told them we would be up for a couple of bottles of wine and not to close before we got there.

We just did this last week! I can't recommend the taxi line enough. There were four of us, though, but even if I were by myself I would do a taxi. This was our firt visit to France, so I know I would have been too nervous to try to navigate the RER. I was overwhelmed enough coming off the Eurostar and entering Paris. Maybe a more experienced traveler would find the RER to be a better option, but for me the $15 or so it cost was well worth it!
(if you are coming off the Eurostar it's super easy to find the taxi line- just go to the front of the train and take a right. Warning- before you leave the building, there will be people calling out "taxi" Do not accept from them. Go to the line and wait-- it goes really fast with a person directing people and drivers)

Thanks, everybody! Taxi it is!