Kea, also called Tzia, is the closest Cycladic island to Athens, a green, hilly island of oak woods, old mule paths and the hill town of Ioulida, much loved by Athenians for weekends. Paros sits in the middle of the Cyclades, so the two are on different ferry lines: Kea hangs off the mainland port of Lavrio, while Paros is served from Piraeus and Rafina.
Our route data lists Blue Star Ferries and Seajets on Paros to Kea, but we could not find a single dated sailing to back that up. Ferryhopper has no page for the pair, our timetable sample holds nothing, and the reverse record even disagrees about the operators. We have not repeated the generic crossing time and fare in those records. If the booking page shows a direct boat on your date, check its stops and duration before trusting it.
In practice, most people go via Athens. Paros to Piraeus runs every day of the year on Blue Star Ferries and Seajets, and Lavrio to Kea runs every day too, with four companies sharing the route. The awkward bit is the transfer between the two mainland ports: Piraeus is on the Saronic Gulf, west of Athens, and Lavrio is south-east of the city, so you need a road transfer across Attica between the ships.
That makes it a full travel day, so consider a night in Athens between the two boats, especially at weekends, when Kea ferries from Lavrio are busy with Athenians. Kea is also linked by ferry with its neighbour Kythnos, a few days a week, which helps if you are combining the western islands.
