In this study, the total phenolic contents and total flavonoid contents of methanol (ASM), chloroform (ASC), and petroleum ether (ASP) extracts of the flowers and leaves of Aster squamatus (Spreng.) Hieron. (Asteraceae) were determined as gallic acid equivalents and quercetin equivalents, respectively. The antioxidant activity of the extracts was determined using three different methods, namely, 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging, the β-carotene-bleaching method, and superoxide anion radical-scavenging activity assay, while antibacterial activity was determined by the disk diffusion method. In the total phenolic and total flavonoid estimations, the richest extract was found to be the ASM extract. The ASC and ASP extracts showed inhibition of below 50% in the DPPH free radical-scavenging method, but the ASM extract, at a concentration ≥500 μg/mL, showed 80% activity. All extracts showed similar superoxide anion radical-scavenging activity, with no significant differences. ASC and ASP extracts showed the highest activity in the β-carotene-bleaching method. In this method, all the extracts showed comparable activity with butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and α-tocopherol standards at a concentration of 500 μg/mL. EC50 values were calculated in the DPPH free radical-scavenging method and the β-carotene-bleaching method. The disk diffusion method, in which no inhibition zones occurred, showed that the extracts had no antibacterial effects on the standard test bacteria Staphylococcus aureus ATCC29213, Klebsiella pneumoniae ATCC33495, Enterococcus faecalis ATCC29212, and Pseudomonas aeruginosa ATCC27853.