Solution polymerization of butyl acrylate and divinylbenzene (DVB) in toluene, initiated with 2,2'-azobisisobutyronitrile and mediated with chain transfer agent dodecanethiol (DDT), was carried out in a capillary microreactor with a 1 mm inner diameter. Through the Strathclyde method, branched poly(butyl acrylate) with different molecular weight distributions (MWDs) was prepared by adjusting the feed formulation and the residence time. The dosages of DVB and DDT were controlled to avoid gelation, and their effects on the branching degree of the products were investigated. The multimodal MWDs were deconvoluted to quantitatively study the branching process. The kinetics in batch and continuous operation are compared. Aqueous miniemulsion polymerization with a similar feed formulation was also conducted in the microreactor, enabling faster reaction rate, lower solution viscosity, and higher branching efficiency. This study demonstrated the feasibility to use commercial monomers to prepare branched polymers with high functionality and a dense architecture in continuous-flow mode.