Providing access to highly diverse polymer structures by multicomponent reactions is highly desirable; efficient Meldrum's acid‐based multicomponent reactions, however, have been rarely highlighted in polymer chemistry. Here, the three‐component reaction of Meldrum's acid, indole, and aldehyde is introduced into polymer synthesis. Direct multicomponent polymerization of Meldrum's acid, dialdehyde, and diindole can perform under mild conditions, resulting in complex Meldrum's acid‐containing polymers with well‐defined structures, and high molecular weights. Additionally, nearly quantitative postpolymerization modification can also perform via this Meldrum's acid‐based multicomponent reaction. These results indicate that Meldrum's acid‐based multicomponent reaction will be a potential tool to prepare novel polymers.