Sweet basil (Ocimum basilicum L.), one of the most widely consumed herbs globally, is used in raw or processed food, and for aromatic essential oils. We investigated the effects of photosynthetic photon flux density (PPFD; 150, 225, and 300 μmol·m⁻²·s⁻¹, herein, referred to as P150, P225, and P300) and red to blue light ratios (R/B ratio) (R:B = 1:4, 1:1, and 4:1, herein, referred to as R/B 0.25, 1.0, and 4.0) with a 16 h light period on the leaf shape and concentrations of functional and aromatic compounds in basil. Total leaf dry weight and leaf mass per area increased with increasing PPFD and R/B ratio. Total leaf area tended to increase with increasing R/B ratio at the same PPFD. Although the highest growth was noted when R/B was 4.0 at P300, the leaves showed ruggedness and curling. β-Carotene concentration based on the leaf dry weight and leaf area at the fourth node increased with decreasing R/B ratio, regardless of PPFD. Concentrations of aromatic compounds (eugenol and linalool) based on dry weight were significantly higher at P150 than at other PPFDs and in treatments with greater amounts of red light. These results suggest that basil growth, appearance, and functional and aromatic compound concentrations can be adjusted as needed by manipulating the PPFD and R/B ratio, although R/B 4.0 at P300 caused malformed leaves.