Petroleum asphaltenes, a by-product of crude oil extraction, are a promising feedstock for the development of high-value carbonaceous materials because of their high carbon content and aromaticity. In this work, we have studied the efficacy of low-value petroleum asphaltenes as raw materials in producing carbon fibers. We present a facile, yet effective, method to produce carbon fibers without the need of expensive pre-treatment processing. To do this, extensive physicochemical characterizations were carried out to evaluate asphaltene properties throughout the entire process. Continuous spinning of green fibers with different diameters (∼10–200 μm) was optimized according to the rheological characteristics of asphaltenes. We originally developed a multi-step stabilization process to cross-link the asphaltene-derived green fibers. This was followed by carbonization of the fibers resulting in fibers with mechanical strength of ∼400 MPa and Young's modulus of ∼70 GPa. These are relatively high values obtained without any pretreatment or high temperature carbonization/graphitization. This study presents a previously unexplored avenue to develop low-cost carbon fibers from low-value petroleum asphaltenes.