Venice and Amalfi Coast

Have you made flight arrangements yet? This is going to be difficult to do these two places. It’s going to be a fairly full day of travel between them. This is also a regular note on this forum, but if you’re counting your arrival/departure days in your nine days then you have less time to work with. Think in terms of nights spent in a place, with two nights equaling one full day of sightseeing. That kind of helps you and the rest of us get a handle on days.

Aside from that, my general advice would be to stick with Venice and somewhere closer (Veneto, Tuscany, Lake Como). You could spend a week plus down Sorrento way, and a day or two would just shortchange both ends. Save it for the next trip.

"nine days"-? -- Doing these two widespread destinations works ( or can work) if you fly into Venice and fly home from Naples. ( or the reverse)

Using other airports for the trip has you spending an inordinate amount of time 'in transit' relative to your total time there.

Assuming 9 days is 8 nights. And if Venice and Sorrento are the places YOU want to visit, it can be done. Just know that you lose most of a day traveling from Venice to Sorrento. You will want to be in the city you are flying home from the night before departure, so fly home from Naples.

3 nights equals 2-2.5 days.

Fly in Venice- 3 nights
First day is jet lag day so hardly counts, 2 days for sightseeing.
Train to Sorrento-via Naples then Circumvesuviana, 4 Nights
First day is mostly travel, 3 days sightseeing allows you to see Sorrento, Pompeii, Capri and some Amalfi coast- or whatever you prefer to see.
Train or ferry to Naples for 1 night
Fly home from Naples

I agree that you are losing touring time for travel. Last year we flew into Venice and loved this magical city. We took a fast train from Venice to Milan (not quite 3 hours) where we took a regional train to Varenna on Lake Como (about an hour.) In my opinion, these 2 locations would provide a romantic trip to Italy. You can return to Milan to fly home. Save a trip to the southern part of Italy and the Amalfi for another trip. You WILL want to return to Italy!! And you will love the Amalfi!! Read up on Venice and Lake Como in the posts here and in Ricks guidebooks. I usually check them out at the library before I purchase the updated version.

Completely feasible and you will love it! We are doing Venice and Sorrento in 8 days and I don’t feel as though this is too much. It is our second time (10 yr anniversary) visiting Italy (first time for our honeymoon we did Venice, Florence, CT & Rome in 10 days...and loved it).
Fly into Rome - stay the night in Rome
Train to Sorrento (via Naples) stay 4 nts
Train to Florence stay 1 nt
Train to Venice stay 2 nts
Fly home from Venice
Not concerned at all about travel times on Train and do not feel rushed. I think you will have lots of time to enjoy, especially if you remove Florence. We thought 1 day in Florence would break up the travel and one day is better than none. You will have a great trip and all the more reason to return- enjoy!

First suggestion is to be honest with yourself about how much time you really have. Stop speaking in vague generalities (ie "I have 9 days"). Provide a specific date of your arrival and a date of your departure, and where specifically you will arrive to and depart from. If you don't have these things 100% nailed down now (which would actually be good), provide proposed dates/places. Without such details, nobody can give you valid advice (because on such a short trip, these details will make all the difference between a reasonable, enjoyable itinerary that makes you happy, and a miserable death-march slog which you would regret).

Venice and Sorrento are located quite distant from each other, which will make the logistics of doing what you propose challenging. Maybe not insurmountable, but maybe difficult and possibly very unwise to attempt. It all depends on the details that you have not yet shared.

Give good details, you'll get good advice.