Being self-incompatible, most Asian plums should be planted with a compatible pollinizer to produce fruits. Therefore, the selection of an adequate pollinizer is essential when new plum cultivars are released. To select a suitable pollinizer for ‘Summer Fantasia’ plum, the S genotype, cross-compatibility, pollen viability, and flowering time of five candidate cultivars were evaluated. Using polymerase chain reaction (PCR) analysis, the S genotype of ‘Summer Fantasia’ was determined as S a S c, which was expected to be compatible with other S genotypes. To test cross-compatibility, the trees were covered with caging net to prevent unintended pollination, and pistils were hand pollinated without emasculation. Fruit set percentage was calculated 10 weeks after pollination. The fruit set percentage resulting from the cross between ‘Summer Fantasia’ and ‘Taiyo’ (S b S c) was 13.8%, whereas that resulting from other combinations was less than 5.0%. Pollen germination percentage was investigated to monitor pollen viability; it varied yearly among cultivars, although ‘Formosa’ (10.6%) and ‘Taiyo’ (13.8%) showed the highest pollen germination percentages among the cultivars. When averaged over three years and two locations, ‘Summer Fantasia’ bloomed 2–3 days after ‘Akihime’, ‘Formosa’, ‘Oishiwase’, and ‘Purple Queen’. Blooming period of ‘Summer Fantasia’ and ‘Taiyo’ overlapped almost entirely. Overall, the results indicated that ‘Taiyo’ was the most suitable pollinizer for ‘Summer Fantasia’.