In 1990, GKS entered their first ever joint venture and global market with Page-Koch Europe Limited, now known as George Koch Sons Europe Limited. They joined a company in the United Kingdom owned by Page Process Systems Limited, dedicated to designing, building, commissioning and servicing paint finishing lines for automobile and major industrial users throughout Europe. With the considerations of ecology, George Koch Sons Europe has designed machines with higher standards of environmentally engineered systems. Robert L. Koch II stated, “the commitment to enter the European market was of great historical significance. Our founder, my great-grandfather, left Europe to seek new opportunities in the United States.” In 1999, James Muehlbauer was elected president of George Koch Sons, and in 2003, Steve Church served as president of George Koch Sons until the end of 2008. Kevin Koch served as interim president from 2009-2012, and Chris Brack served as president from 2012- 2019. Dan Hoefling served as the president of what is now known as Koch Finishing Systems, previously George Koch Sons, from 2019-2023. In 2024, Josh Gilberg began serving as president. 

Koch is the fourth oldest distributor of Carrier equipment and has long been recognized as a supplier of top-quality HVAC equipment. In 1991, Koch Air Conditioning, now known as Koch Air LLC, sold their air conditioning installation business to concentrate on distribution. In 1994, Koch acquired the Carrier distributors in Indianapolis and Louisville owned by Carrier and in 1996 acquired Marco Sales, a Carrier distributor based in St. Louis. George Koch Sons has expanded to own four Carrier franchises that distribute and service Carrier products in Indiana, Kentucky, Illinois, and Missouri. In 2011, Koch Air opened an office in Lexington, KY. James Muehlbauer served as president of Koch Air from 2003 until the end of 2011. In 2012 Jim's son, Brad Muehlbauer, became president.

In 1996, Koch Enterprises entered its second joint venture with the David J. Joseph Company, the largest ferrous scrap broker and processor in the US and elected Jim Butkus as president. Koch Enterprises became the full owner of Audubon Metals in 2004. In 2017, Brian Hawkes became president. Audubon Metals LLC is located in Henderson, Kentucky. The company processes automobile shredder residue (Zorba) and produces aluminum alloy for the manufacture of die castings. Audubon Metals purchases Zorba from shredder yards throughout the US. Using a unique process, Audubon removes the aluminum from the Zorba and smelts it into alloys used for die casting. This aluminum is sold in molten form to die casters throughout the midwest including Gibbs Die Casting.

In 2006, Koch Enterprises, Inc. diversified its portfolio of companies by acquiring South Western Communications (SWC), a technology company that offers building security, communications and control systems for healthcare, educational, commercial, industrial and detention applications. Randy Miller founded the company in 1976 in Evansville and his son-in-law, Todd Lucy, became the president with the transition of ownership. In 2009, SWC purchased Suwanee, GA, based Richardson TSI to form SWC-Richardson Technology Systems which will continue to expand its healthcare and education services in Georgia.

In 1999, Koch Enterprises, Inc. was formed as a holding company for George Koch Sons and the other subsidiaries. Koch Enterprises is now being led by the fifth generation, the great-great-grandson of the founder George, great-grandson of Louis J., Sr., grandson of Robert L. Koch and son of Robert L. Koch II, Kevin R. Koch.