One new dimeric bromopyrrole alkaloid, agelanemoechine, with an unprecedented imidazo [1,5-a] azepin nucleus together with one known dimeric bromopyrrole alkaloid sceptrin were isolated from the marine sponge Agelas nemoechinata. The structure elucidation and absolute configuration assignments were determined by extensive spectroscopic analyses and the comparison of experimental and calculated ECD. Agelanemoechine showed strong pro-angiogenic activity in zebrafish. © 2019 American Chemical Society.