Ocimum species are used in traditional Iranian medicine, as a culinary herb, and as a well-known source of flavoring principles. Horticultural characteristics, including quantitative and qualitative traits along with the chemical variation of phenolic acids, of 23 accessions of basil (Ocimum basilicum L.) from Iran were studied. Morphological studies of accessions showed a high level of variability in recorded traits. Quantification of phenolic acids was determined using high-performance liquid chromatography and showed drastic variations between accessions. Chemical studies revealed that rosmarinic acid is the predominant phenolic acid present in both flower and leaf tissues. Unusual basil accessions were identified that can serve as genetic sources of phenolic acids for crop improvement.