Cucumber green mottle mosaic virus (CGMMV) is a devastating cucurbit disease, first reported in the U.S. in 2013. The damage to host plants and fruit can be extensive, resulting in substantial yield and quality loss. Although contaminated seeds are considered an important way to introduce the virus into new production fields, the potential of CGMMV particles from naturally-contaminated seeds to start a new epidemic is not fully understood. The objective of this study was to investigate the viability of the virus recovered from naturally-contaminated cucurbit seed samples by bioassay. Two CGMMV-positive cucurbit seed samples were used, one squash and one melon. Twenty subsamples, containing 100 seeds each, were tested by ELISA to confirm the presence of the virus. The squash and melon seed samples presented medium (12/20) and high (17/20) CGMMV contamination levels, respectively. Nicotiana benthamiana was initially used to assess the pathogenicity potential of extracted CGMMV sap from contaminated seeds. Plants inoculated with extraction buffer (PBS) and viable CGMMV particles were used as mock- and positive-controls, respectively. Typical leaf distortion and blistering were observed only on the indicator plants inoculated with extracts from melon seeds and positive control. Vertical transmission of the virus was only detected from the positive control. Additional pathogenicity tests on cucumber (‘Straight 8’), melon (‘Expedition’), and watermelon (‘Sugar Baby’) are underway.