Suggestions for rental car Athens to Nafplio?

The airport is outside the city so does not involve city driving. So rent at the airport. Purchase or bring a decent road map. We were not given one by rental agency and got lost. Well marked until Corinth and after that you need to know what cities are in the same direction as Nafplio to get off at right exit. Nafplio is not on tollway signs.

Uber does not operate in Greece.

Definitely rent a car from Athens airport. You are immediately on the National road, a very good 4 lane highway from the airport all the way to Corinth. (Korinthos) It is a toll road so be sure to have some cash.
Its a good idea to have a paper map with you just to check the GPS occasionally. The turn off the National road for Nafplio is after you pass Corinth. That turn off is also where you can find Ancient Nemia. It was a sister city to Olympia and still has its stadium, a partially restored temple and a decent small museum. Its well worth an hour stop.

The drive to Nafplio is on a secondary paved road with gentle hills as you drive through the Nemian wine country.
When you reach Nafplio there is a large free parking lot at the seaside.

Re Car rental. We have used ACR Athens Car rental. They have a good web site. It is a local company not one of the big international companies. I have found local companies work hard for your business.
ACR has a different business model than we see in North America. They do not have an airport location. They monitor your flight arrival and when it arrives they bring the car to the airport and meet you at arrivals door. The driver will have a sign with your name on it. You will be taken to the airport parking lot where you will inspect the car complete the paperwork on the hood of the car and away you go. When you make your booking you may be able to request they provide a map with the car.
There are several local companies that use the same business model but I have not used them just ACR.

For fun here is what you are going to see.
Nafplio and Peloponnese http://www.flickr.com/photos/stanbr54/sets/72157632094108982/

We used ACR. We asked for a map but they didn’t have one to give us. Fine otherwise but I again I would make sure you have a map.

Just reiterating: you are immediately on the highway and bypass city driving, and it's an easy-two hour drive. I used google maps on my phone (have free data with T-Mobile), navigating while husband drove.
Had a fine experience with Hertz. The only hazard we encountered in 9 days driving the Peloponnese was the occasional large turtle on the roadway.

I agree. Pick up your car at ATH and easily drive to beautiful Napflion. There is so much to see the surrounding area and this small waterfront city is a real gem.

Well, if you plan on driving to Nafplio and staying, I'm not clear if a car is necessary. We took the bus from Athens to Nafplio, and it was convenient and easy to take. On the next day in Nafplio, we took another bus to Micinae, and this also worked fine. I'd do a car if non-major sites are in your playbook, but most places we wanted to go to in Greece were easily accessed using the bus.

Paul, that decision about KTEL bus vs car rental depends very much upon how many days the OP has allotted to Nafplio -- This is why it's so frustrating when people want good & specific advice, yet don't include key info like How Many Days? Why? Because if you have 4-5 days, you can use local busses & take one day for Mycenae, another for Epidaurus etc etc. The local busses do go there, but are NOT well-scheduled so you can do Mycenae 9 - 12, return to Nafplio and get another bus to Epidaurus 1- 4 pm. You can only do 1 site per day via bus. If you have a car & time is short, in a day you can do both of these... and with early start maybe even stop for 45 minutes to see Tiryns (I call such days a Ruin-a-thon... and by 4 or 5 pm, you'll need a swim.... try Asine's tiny cute beach).

Another thing that would govern choice of bus vs. car is date of trip... if it's from this week on, thru Sept 1 at least, it will be SO hot from 12-4, that essentially one must hide from the heat, either under a beach umbrella, by a pool, in a museum or one's a/c hotel room. An a/c car is a help. If going during milder weather, one can site-see most of day, covering more in fewer days. However, TravelBug has given us NO clue as to whether their trip is in Height of hot season, or in the fall... or next Spring for that matter. How about some clues, T-B? We are experienced, but are not mind-readers. Share more!

Agree with earlier posts about picking up at the Athens Airport. We had a very competitive rate from Athens Car
Rental and were pleased with their service. Will rent from them again. Interesting response to this question from "Janet". If you are so frustrated by a person's question, that you feel the need to respond in such a snarky manner, then perhaps you should stick to questions that you feel are appropriate. Always choose kindness.

Sorry HH for my abruptness, perhaps I was too concerned w getting the point across that one may encounter pitfalls if taking advice not based on full knowledge .... specifically, if new tourists are short on time. it can be VERY frustrating and difficult to reach Argolid-area sites efficiently by local transport, as suggested by Paul, due to the uncooperative bus timetables. And because there wasn't the right info from TravelBug to know which category they fall into, I was frustrated as to which strategy to advise.

In Oct 2018, we rented a car from Enterprise at the airport. Have used Enterprise in USA for years. Easy procedure out & return. They upgraded us to a better car without cost. Used car for day trips to Mycenae, etc. Easy driving everywhere. Traffic & map mis-read on highway returning put us into downtown Athens at rush hour. Interesting experience - had visions of buying the new Mini, but all went well. Greek drivers careful with their cars - scooter riders not so much. Later read that car entering round-about has right-of-way. (Different than else where.) Maybe that accounted for a long horn honk once.

@janet: We did consider the theatre at Epidurus, but as you said on public transit, not possible in one day. However, just to note, buses are very reasonable. Cost is only one feature, but the full cost of Athens-Nafplio-Athens and Nafplio-Micinae-Nafplio was 30.2E/person.

Thanks, Janet, for suggesting Nafplio. It was the highlight of our Greece leg.