Travel from Trouville (Normandy) to CDG – how and when?

If I were you, I would stay in Paris Wednesday night.

It would technically be possible to get from Trouville to CDG on the same day -- depending on the exact day, there is usually a 7:27 departure from Trouville-Deauville that gets into Paris St-Lazare at 9:38, which would give you plenty of time to change stations in Paris and catch the RER out to the airport.

However, I personally wouldn't want to be to be so far away from the airport the morning of a long international flight. There is one later train involving a connection that you could presumably take (the 8:00 which arrives at 10:30 with a change of train in Lisieux) but after that you are cutting it too close -- Trouville/Deauville is on a single-track spur off the main French railway network, so rail service to/from the city is not very frequent.

A 3 pm flight is definitely late enough that you don't have to stay at the airport and can choose how you want to get out from Paris to the airport, via RER/bus/taxi depending on your preferences.

I agree with Andrew.

Trouville and Deauville are attractive resort towns. There's rail service via inexpensive TERs direct to Paris, so you wouldn't even need to lock down your travel plans in advance.

A bus ride away to the west is another attractive resort town, Cabourg. From there you could either backtrack to Deauville-Trouville to pick up the TER to Paris or go further west to Caen and get a train from there.

Many people on the forum have been to Honfleur and enjoyed it. It's a bus ride east of Deauville-Trouville. To get to Paris from Honfleur, you could take a bus a bit farther on to Le Havre and pick up a TER to Paris. There may also be bus service from Honfleur to Paris, but I don't imagine it's frequent.

Thanks! You confirm my gut reaction of getting to Paris on Wed evening. We'll be staying in these towns during our bike tour: Carentan, Bayeux, Courseules sur Mer, Cabourg, Honfleur and then circling through the countryside back to Trouville to end.
I had thought about Rouen for Wed night, but too far for Thursday travel to CDG. I also thought perhaps take the bus from Trouville to Rouen or to Caen and explore a bit, and then on to Paris in the evening.

Caen has an impressive, comprehensive Peace Museum where you could spend the entire day, but nearly the entire city was flattened during the war, and it's one of France's least attractive from a superficial standpoint. Rouen is much, much more attractive. I'd head there for the day if you can make the transportation work for you. Do Google to be sure there's a place to store your luggage.

Always be in the city of a high stakes flight the night before -- because your flight is in the afternoon I would aim to be in Paris by afternoon and plan a nice last evening and meal and walk along the river and then a leisurely morning, getting on the train to CDG at 11 or so, or getting a cab then. If you choose a hotel near the RER B then it is an easy shot to the airport -- if you have a lot of stuff you could take a cab for 53 plus reservation fee of 7 Euro if you are on the right bank -- 5 euro more from the left. Book the night before on G7 english speaking phone line.

We often stay at Henri IV Rive Gauche when we have a single night in Paris -- it is near the St. Michel RER station. It is on the left bank though for cabs.