One-bottle universal adhesives have been widely used because of their simplicity of bonding procedures for various dental materials. The present study evaluated the effect of the polymerization light source on the micro-tensile bond strengths of a universal adhesive (Clearfil Universal Bond Quick) to dentin in comparison with a one-bottle self-etch adhesive (Clearfil S-3 Bond Plus) and two 2-step self-etch adhesives (Clearfil SE Bond and Clearfil SE Bond 2). The adhesives were applied to extracted human dentin according to the manufacturer's instructions and irradiated using either a quartz-tungsten-halogen (QTH) or blue light-emitting diode (LED). Subsequently, a resin composite was incrementally built on each adhesive and light-cured using the QTH. The bonded specimens were sectioned and subjected to micro-tensile bond strength tests. Both the type of adhesive and the light source were found to statistically affect the bond strength, with no interactions. The LED gave greater bond strength than the QTH. The bond strengths of the two-step adhesives were significantly higher than those of the one-bottle products, irrespective of the light source. The Clearfil Universal Bond Quick exhibited significantly higher bond strength than the Clearfil S-3 Bond Plus. LED curing improved the performance of Clearfil Universal Bond Quick, and this product generated bond strength superior to that of the existing one-bottle adhesive Clearfil S-3 Bond Plus.