Provided is a resin composition exhibiting inhibited generation of defects in thermoforming, and having a superior appearance and sufficient strength. Also provided are a multilayer structure and a thermoformed container that exhibit superior appearance characteristics and impact resistance even when a recovered material obtained by repeatedly recovering a remnant, a scrap and the like of a sheet containing the resin composition is used. The resin composition contains: an ethylene-vinyl alcohol copolymer (A); a polyolefin (B); and a carbonyl compound (C) having 3 to 8 carbon atoms. The carbonyl compound (C) is an unsaturated aldehyde (C-1), a saturated aldehyde (C-2), a saturated ketone (C-3) or a combination thereof, and the content of the carbonyl compound (C) is 0.01 ppm or greater and 100 ppm or less.