Has anyone made a day trip to Giverny from Paris by train on a Sunday? We are interested in doing this on June 20th, would like to get an early start, and have heard that there is a train from St. Lazare station. Would appreciate any information from someone who has been there, done that. Thanks!

yes, I have done that. There are trains on Sunday from St Lazare at 8:06, 9:32 and 10:44 am. The trip takes bout 45 min. I think the 8:06 train would be the one you want, as Monet's gardens open at 9:30. They used to close for a couple hours in the middle of the day (noon to 2, as I recall), but I think they don't do that any more. If you get there early, that won't be a problem, anyway. From the train station, you can take a bus or taxi to MOnet's home. Be sure to check return train schedule times as there aren't that many later in the afternoon. There is one at 12:41, 3:35 and then none until 5:30 or so.

I made this trip on a Sunday in April. There were only 2 departures, so definitely check the schedule,and the trains leave promptly. Please note, once you get to the Giverny train station, you'll need to get to the town, but the bus stop is not the one withthe shelter right outside the station, but several feet away on the right, and there are no signs to indicate this. We hopped a ride for 1.20e with a bus that looks like a tour coach bus. You can catch this same ride from the Giverny parking lot to the Giverny train station. It is not walking distance from the train station. You really need to get to Monet's house & gardens before 1:00 to avoid long lines, and as mentioned the doors open at 9:30. We had stayed overnight, and were inside by 9:30, having the gardens to ourselves for almost 2 hours, (with only about 20 others there). You cannot purchase a ticket in advance for Monet's house, but you can do so for the Museum of American Artists,which is small and can be covered in about 2-3 hours. They have a nice outdoor patio. Any other questions, feel free to ask.
If you decide to stay overnight, it is relaxing, tranquil and inexpensive, and I recommend La Musardiere, where I stayed.

Thank you Christina and Ninasdream for the information and tips you provided! We are tight for time on our itinerary, so this assures that we will be able to fit in a visit to Giverny before our departure from Paris Tuesday (since Giverny is closed on Monday.) This site is a wealth of information, so thanks to all you Fodorites who share your experiences.

It has been a while since I last went, but my previous experience was that taxis were few and far between early on a weekend morning in Vernon, which is where the train from Paris takes you.
So I'd look into the bus. You could call a taxi in advance (from the museum shop) to come get you to take you back to the train station.

Har - maybe call ahead and doublecheck on the Monday closings, because I was there on from Sunday to Easter Monday, and the information center told me that they have begun opening on Mondays- we went to both the Monet house and the Museum of American Artists. Glad to be of help. Enjoy!