The closest beach to Paleokastro (Mainland Halkidiki) is Agios Mamas, 11.5 km away. Ordered by distance from Paleokastro. Photos, map, reviews.
11.5 km from Paleokastro

13.1 km from Paleokastro

14.7 km from Paleokastro

14.8 km from Paleokastro

17.0 km from Paleokastro

19.0 km from Paleokastro

20.7 km from Paleokastro

21.6 km from Paleokastro

23.3 km from Paleokastro

45.6 km from Paleokastro

46.9 km from Paleokastro

47.7 km from Paleokastro

Agios Mamas, just 11.5 km from Paleokastro. The rest are listed below, ordered by distance.
Within 15 km of Paleokastro there are 4 beaches, with 21 across Mainland Halkidiki in total.
Based on user reviews: Nea Moudania (★4.0), Plagia-Flogita Beach (★3.8), Portes (★3.8).
The beaches are spread out around Paleokastro. A car makes exploring much easier — local buses and taxis are limited outside peak season.
Paleokastro is on the Mainland Halkidiki side of Halkidiki, in northern Greece. The nearest airport is Thessaloniki (SKG); from there a car is the most convenient way to reach the Mainland Halkidiki villages.