LED assemblies and related LED light bulbs. An LED assembly has a flexible, transparent substrate, an LED chip on the first surface and electrically connected to two adjacent conductive sections, a first wavelength conversion layer, formed on the first surface to substantially cover the LED chip, and a second wavelength conversion layer formed on the second surface. The flexible, transparent substrate has first and second surfaces opposite to each other, and several conductive sections, which are separately formed on the first surface.