Archaeological excavations in two coastal sites of Greece, Ftelia on Mykonos and Cyclops Cave on Youra, have provided suitable material (charcoal/marine mollusk shell paired samples deposited simultaneously in undisturbed anthropogenic layers) to estimate regional changes of the sea surface radiocarbon reservoir effect (ΔR) in the Aegean Sea. Moreover, pre-bomb 14C ages of marine mollusk shells of known collection date, from Piraeus and Nafplion in Greece and Smyrna in Turkey, also contributed to the marine reservoir calculation during recent years. In this article, these already published results, 10 in total, are considered and calibrated again using the latest issues of the calibration curves IntCal13 and Marine13. The same calibration data were applied to 11 more paired samples from the archaeological sites of Palamari on Skyros and Franchthi Cave in the Argolic Gulf, published here for the first time, in order to investigate the fluctuation of the reservoir ages R(t) and ΔR values in the Aegean Sea from ∼11,200 BP (∼13,000 cal BP) to present. Our data show that R(t) and ΔR values are not constant through time and may vary from 1220 ± 148 to −3 ± 53 yr and −451 ± 68 to 858 ± 154 14C yr, respectively. An attempt was also made to correlate these fluctuations with eastern Mediterranean paleo-environmental proxies and other relevant paleoceanographic data found in the literature.