Technical Abstract: Seedless triploid watermelons have increased in popularity since the early 1990’s, and the demand for seedless fruit is on the rise. Sweetness and sugars are crucial breeding focus for fruit quality. Volatiles also play an important role, yet, we found no literature for seedless varieties, and no reports using solid phase microextraction (SPME) in watermelon. The objective of this experiment was to identify volatile and semi-volatile compounds in 5 seedless watermelon varieties using Carboxen/DVB/PDMS SPME with GC-MS. Fully ripe, 2-day old fresh watermelons, were sanitized, rinsed, and the rind removed with a sharp knife. Thick slices (5 cm) were cut and placed on a Silver King Kutlett to cut 2.5 x 2.5 x 5.0 cm bars. Three bars were combined and squeezed through miracloth to produce rapid juice extracts for immediate headspace SPME GC-MS. Aldehydes, alcohols, ketones, and 1 furan (2-pentyl furan, a lipid oxidation product) were recovered. Based on total ion count peak area, the most abundant compounds in 5 varieties were 3-nonen-1-ol/(E,Z)-2,6-nonadienal (16.5 – 28.2%), (E)-2-nonenal (10.6 – 22.5%), and (Z)-6-nonenal (2.0 – 11.3%). Hexanal was most abundant (37.7%) in one variety (Pure Heart). The most abundant ketone was 6-methyl-5-hepten-2-one (2.8 – 7.7%). Some sensory attributes reported for these compounds are melon, citrus, cucumber, orange, rose, floral, guava, violet, vegetable, green, grassy, herbaceous, pungent, fatty, sweet, and waxy. Identifying and relating these compounds to sensory attributes will allow for future monitoring of the critical flavor compounds in seedless watermelon after processing and throughout fresh-cut storage.