||The cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), is a limiting pest of many agricultural crops worldwide. At present, in-field populations of H. armigera are routinely monitored using conventional light traps. During 2014, 2015, we conducted field assays to assess the relative attractiveness of narrow-band light-emitting diodes (LEDs) at 19 single wavelengths (375–748 nm) in H. armigera light traps. Between 2016 and 2019, LEDs with the most attractive wavelengths were then further evaluated in two different sites, i.e., Xinxiang and Anci (China). During 2014–2015, the highest H. armigera trap capture was obtained with LEDs at 395 nm, while it was not significantly different from LED wavelengths of 375 nm and 418 nm in 2015. During field trials in Xinxiang, H. armigera trap capture did not differ among (four) wavelengths (375 nm, 385 nm, 395 nm, and 405 nm) in either year. In the Anci site, most H. armigera adults were caught in traps equipped with LEDs of 385 nm during two years, but it was not significantly different from those at 405 nm in 2017. In 2019, H. armigera trap capture rate was higher for LEDs at 385 nm than for those at 395 nm, and 2.91-fold higher to that of a commercial UV blacklight (365 ± 50 nm) trap. Our work shows how LED-equipped traps constitute an efficient, energy-conserving way to monitor cotton bollworm populations, providing trap capture rates that surpass those of conventional technologies. We discuss how these innovative measures can complement the integrated pest management (IPM) toolbox for H. armigera in China and abroad.