Eight new angucyclic quinones, miaosporones A to H (<b>1</b>-<b>8</b>), along with the previously described metabolites 8-hydroxy-3-methylbenz[<i>a</i>]anthraquinone (<b>9</b>), tetrangulol (<b>10</b>), 5,6-dihydro-1,8-dihydroxy-3-methybenz[<i>a</i>]anthracene-7,12-quinone (<b>11</b>), and SF2315A (<b>12</b>), were isolated from the terrestrial actinomycete <i>Actinomadura miaoliensis</i> TBRC 5172 obtained from sediment collected from the Huai Yang reservoir, Prachuap Khiri Khan Province, Thailand. The relative and absolute configurations of the new compounds were determined from analysis of NMR spectroscopic and X-ray crystallographic data. Miaosporone A exhibited antimalarial activity against <i>Plasmodium falciparum</i> K1 and antibacterial activity against <i>Mycobacterium tuberculosis</i> with respective IC<sub>50</sub> values of 2.5 and 2.4 μM and displayed cytotoxic activities against both cancerous (MCF-7 and NCI-H187) and nonmalignant (Vero) cells.