The present study investigated phenolic compounds and enzymes involved in female fertility in banana plants of the Cavendish subgroup. The wild diploid Calcutta 4 and commercial cultivar Grand Naine (Cavendish subgroup) were used. The following five stages of floral development were proposed: S1 (partial vertical emission), S2 (total vertical emission), S3 (total horizontal emission), S4 (pre-anthesis), and S5 (anthesis). Following collection, pistillate (female) flowers were freeze-dried for the subsequent removal of nectaries and the analysis of phenolic compounds (PCs), antioxidant activity (DPPH and ABTS), enzymatic activity [peroxidase (POD) and polyphenol oxidase (PPO)], and total proteins (TPs). The highest values were recorded at the S3 stage, with the values decreasing as the stages progressed (until S5). At the S3 stage, the following results were obtained for Calcutta 4 and Grand Naine, respectively: PCs (32.4 and 36.1 mg GAE·g−1); DPPH (735.2 and 454.4 µM TE·g−1); ABTS (647.8 and 555.5 µM TE·g−1); POD (0.8 and 0.7 µmol·min−1·g−1); PPO (3.7 and 2.7 µmol·min−1·g−1); and TP (3.2 and 2.4 µmol·min−1·g−1). These results indicate that PCs and enzymes regulate female fertility, suggesting that crossbreeding should be performed from the S3 stage in cultivars of the Cavendish subgroup to achieve fruits with seeds.