A descriptive analysis was conducted comparing schemes, crimes, and techniques used by far-rightists, Islamic extremists, and non-extremists, before moving into an in-depth social network analysis of their relational ties in co-offending, business, and family networks. The descriptive findings revealed considerable differences in the modus operandi followed by far-rightists and Islamic extremists as well as the prosecutorial strategies used against them. The subsequent exploratory and statistical network analyses, however, revealed interesting similarities, suggesting that financial schemes by political extremists occurred within similarly decentralized, self-organizing structures that facilitated exchanges between individuals acting within close-knit subsets regardless of their ideological affiliation. Meaningful interactions emerged between far-rightists and non-extremists involved in business ventures and within a tax avoidance scheme, indicating that the crime-extremism nexus was more prevalent within far-right settings compared to Islamic extremist ones. Financial crime poses a serious threat to the integrity and security of legitimate businesses and institutions, and to the safety and prosperity of private citizens and communities. Experts argue that the profile of financial offenders is extremely diversified and includes individuals who may be motivated by greed or ideology. Islamic extremists increasingly resort to typical white-collar crimes, like credit card and financial fraud, to raise funds for their missions. In the United States, the far-right movement professes its anti-government ideology by promoting and using a variety of anti-tax strategies. There is evidence that ideologically motivated individuals who engage in financial crimes benefit from interactions with profit-driven offenders and legitimate actors that provide resources for crime in the form of knowledge, skills, and suitable co-offenders. Attribute and relational data were extracted from the U.S. Extremist Crime Database, which is the first open- source relational database that provides information on all extremist crimes, violent and non-violent, ideological and routine crimes, since 1990.