Viola has launched a number of businesses during his career. In 1987, he founded Pioneer Futures, one of the top fifty futures commission merchants in the US. In 1988, he founded The Independent Bank Group, a Texas-based regional bank which is listed on NASDAQ (IBTX). Viola was also one of the two partners who launched EWT, LLC and Madison Tyler, LLC, two electric trading firms formerly based in Beverly Hills, CA and was able to use the electronic trading technique to his own personal gain making him one of the richest men in the world. In 2008, Viola founded Virtu Financial, active in electronic market making. Viola took Virtu Financial public in April 2015, trading as a NASDAQ listed company (VIRT).