Objective: To evaluate the amount of residual monomers released after polymerization by the compomers in different colors and viscosities over time. Material and Methods: The compomer samples of different colors and viscosities (flowable compomers; blue-pink and packable compomers; A2-blue-pink-gold) were prepared in molds with an inner diameter of 5 mm and a height of 2 mm. In polymerization of samples, a LED unit was used. The amount of monomers released from the samples kept in 75% ethanol/water solution was measured by a high-performance liquid chromatography (HPLC) instrument in the 10th minute, in the 1st hour, and in the 1st, 7th, and 14th days. For statistical analyses, the paired sample t-test, independent sample t-test, and one-way ANOVA with Tukey's post hoc test were used. Results: The amount of residual monomers released from all materials increased over time. At the end of the 14th day, the most released monomer from all compomer samples was BisGMA. The total amounts of released monomers from the packable compomers were Gold>A2>blue>pink. The amount of residual monomers released from flowable compomers was higher in blue than in pink. Conclusion: The color and the viscosity are the factors affecting the residual monomer release in compomers.