Metastasis is a key driving force behind the high mortality rate associated with lung cancer. Herein, we report the first study revealing the antimetastasis activity of jorunnamycin A, a bistetrahydroisoquinolinequinone isolated from a Thai blue sponge Xestospongia sp. evidenced by its inhibition of epithelial to mesenchymal transition (EMT), sensitization of anoikis, and suppression of anchorage-independent survival in human lung cancer cells. Treatment with jorunnamycin A (0.05-0.5 μM) altered the expression of p53 and Bcl-2 family proteins, particularly causing the down-regulation of antiapoptosis Bcl-2 and Mcl-1 proteins. Under detachment conditions for 12 h, jorunnamycin A-treated cells exhibited diminution of pro-survival proteins p-Akt and p-Erk as well as the survival-promoting factor caveolin-1. Corresponding with the inhibition on the Akt and Erk pathway as well as activation of p53, there was an increase in the epithelial marker E-cadherin and a remarkable decrease of EMT markers and associated proteins including vimentin, snail, and claudin-1. As the loss of anchorage dependence is an important barrier to metastasis, the observed inhibitory effects of jorunnamycin A on the coordinating networks of EMT and anchorage-independent growth emphasize the potential development of jorunnamycin A as an effective agent against lung cancer metastasis.