Abstract: The effective detection of X-ray radiation with low threshold is essential to many medical and industrial applications. Three-dimensional (3D) organolead trihalide and double perovskites have been shown to be suitable for direct X-ray detection. However, the sensitivity and stability of 3D perovskite X-ray detectors are limited by ion motion, and there remains a demand to develop green and stable X-ray detectors with high sensitivity and low detection limit. The emerging low-dimensional perovskites have shown promising optoelectronic properties, featuring good intrinsic stability and reduced ion migration. Inspired by this, we show that our 2D layered perovskite-like (NH4)(3)Bi2I9 device provides unique anisotropic X-ray detecting performance with different crystal directions, effective suppression of ion migration and a low detection limit of 55 nGy(air) s(-1). These results will motivate new strategies to achieve a high-performance X-ray detector by utilizing 2D layered perovskite or perovskite-like materials, without requiring toxic elements.