Logistics Question for Ferry Vs. Airplane to Milos

I don't know how many passengers you are, but I tried with 2 passengers with Aegean and Sky Express and there are still seats available on flights to Santorini on May 29th on more than 10 flights between 10:00 and 16:00.

The 9:00 a.m. Seajets ferry to Milos costs €79 per passenger.

Hi JoLui - Thanks for the response, but I'm not sure how getting to Santorini would help me? It looks like it's a 2 hour ferry from there to Milos. Maybe I am missing something! There are only about six flights to Milos and four are sold out, which seems to be the case on lots of days in late May, not just the 29th.

I am really wondering if anyone has experience getting to the ferry and to the airport from the west, and if one is more efficient or less hectic than the other? I have never been there before and thought someone might have an opinion about it.

Oops, sorry.
Why did I read Santorini instead of Milos? No idea... maybe the wine...

Yes, the drive is shorter from Nafplio to Piraeus. The issues you might encounter are the morning traffic jams upon arriving in Piraeus. To allow for a minimum safety margin, I think you should leave Nafplio around 5:30 a.m.
If you can return the car to the port of Piraeus, the security procedures for boarding the ferry are nonexistent. You just need to be at the dock ready to board, say 10 minutes before the ferry departs. But be aware that the ferry doesn't wait for latecomers. It leaves on time.
The port of Piraeus is huge. There are about 4 kilometers of docks. Seajets ferries to the Cyclades depart from Gate E9, which is located here:

https://maps.app.goo.gl/G5vQjsijxcik8UkcA

Street view:

https://maps.app.goo.gl/MGfoB8VQhWDWuKyM9

If you are returning the car in Piraeus, contact the rental company, specify this gate, and arrange a drop-off location. You should be able to return the car to the docks near the ferry.

Note that on May 29th, you can also take the Minoan Lines Festos Palace ferry at 9 PM.

https://www.ferryhopper.com/en/#/results?itinerary=PIR%2CMLO&dates=20250528

Advantage: Only €44 per passenger, no more hassle with the trip to the port, no need to get up in Nafplio at 4 AM, you could spend a large part of the day strolling around Nafplio (or anywhere else between Nafplio and Piraeus).

Disadvantage: you'll be in Milos at 1 AM (hotels are used to these late arrivals).

The journey to the airport is a little longer, and you may also encounter traffic jams. You'll need to allow for some time for the procedures, which can take longer than in Piraeus depending on the rental company and the location where you return the car (finding the right parking). Then, be at the airport building at least 1 hour before takeoff, or 1.5 hours if you have luggage to check in.

All that being said, there is still an (expensive) option if you're flying to Santorini: once in Santorini, you can arrange a transfer from the airport to the port and take one of these two ferries to Milos:

https://www.ferryhopper.com/en/#/results?itinerary=JTR%2CMLO&dates=20250529

The transfer time from the airport to the port by taxi will take about 30 minutes (around €40).

The ferry ticket costs €93.70 per passenger (yes, Seajets ferries are overpriced), add the €40 taxi fare, plus the cost of the flight to Santorini.

So, 4 options. It's up to you.

Thanks so much JoLui! That is extremely helpful. I hadn't considered the 9pm ferry and we were tempted by such a leisurely day. But it turns out that my husband strongly prefers a flight so we'll probably end up booking the 9:30am (assuming it's not sold out by now :) We don't check bags and will have rented the car in the same spot, so familiarity with the location should help reduce our stress with the return. And we'll be taking a ferry later on from Sifnos, so we will get to experience all of that. I had no idea these specific flights would sell out, so lesson learned! And thanks for the suggested arrival timing. Every airport is so different...

Flights to Milos are operated on ATR turboprops with only 42 seats (approximately). Therefore, flights are sometimes sold out.

You might be in luck, Aegean just started a flash sale this morning!
Don't wait!! Your 9:35 flight is 40% off, there are also seats on the 5:55 p.m. flight (also 40% discount). Seats will sell out quickly.

https://en.aegeanair.com/flight-deals/offers-competitions/flash-promo/

Also note that carry-on baggage on flights operated with ATR cannot exceed 55cm x 40cm x 23cm and 8 kg.

These sizes are smaller than the usual size on Airbus A320s.
Upgrade to a Comfortflex ticket for €6 more if your baggage exceeds these sizes and weights; otherwise, you'll pay a significant surcharge at check-in.

Flights booked! A better deal is a slight consolation for such an early morning. :)