The plant hormone ethylene and the gaseous signaling molecule nitric oxide (NO) are involved in numerous plant growth and development processes. However, the mechanisms by which their interaction affects adventitious root development in plants is still not adequately studied. In this experiment, the interaction of ethylene and NO in the adventitious rooting process of marigold (Tagetes erecta L. cv. Marvel) was investigated. Treatments with different dosages of ethylene-releasing ethephon (Ethrel^®, Bayer Crop Science, Leverkusen, Germany) significantly affected the formation of adventitious roots. The greatest rooting ability was observed in 10 μM ethephon-treated explants. It was further shown that the effect of ethylene could be blocked by the specific NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), nitric oxide synthase (NOS), enzyme inhibitor N^G-nitro-l-Arg-methyl ester (l-NAME), and nitrate reductase inhibitor (NaN₃). Moreover, ethephon treatments induced an increase in the endogenous NO levels and significantly improved activities of NOS and nitrate reductase (NR) during rooting. Thus, the induction of adventitious roots by ethylene may be through enhancing the levels of NO. Enzymatic pathway NOS and NR could be responsible for ethylene-induced NO production. Furthermore, ethylene and NO treatments at the appropriate dosage may increase the activities of indoleacetic acid oxidase, peroxidase, and polyphenol oxidase. Our work suggests that the stimulation of adventitious roots by ethylene relies on internal generation of NO.