Organic solar cells (OSCs) have been considered as a promising, cost-effective alternative to the silicon-based solar cells due to their light weight, mechanical flexibility, and easy fabrication features. Over the past decades, organic semiconducting materials have been developed rapidly for use in bulk heterojunction (BHJ) OSCs. Among them, porphyrin-based small molecules have been widely applied as electron donors and electron acceptors in BHJ OSCs due to their large conjugated planar structures and strong UV-visible and near-infrared absorption. In this short review article, we mainly focus on summarizing the recent progress of the rational design of push–pull porphyrin-based small molecules for BHJ OSC applications. After various structural developments, the power conversion efficiencies (PCEs) of porphyrin-based small molecules as electron donors in OSCs have exceeded 12%. Apart from that, a PCE of 9.6% has been recorded for a device based on a porphyrin electron acceptor. This paper will provide a good insight into the structure–performance correlation and molecular engineering strategies of porphyrin-based small molecules in a stepwise manner.