Ambani later enrolled for an MBA at Stanford University but withdrew in 1980 to help his father build Reliance, which at the time was still a small but fast-growing enterprise. His father felt that real-life skills were harnessed through experiences and not by sitting in a classroom, so he called his son back to India from Stanford to take command of a yarn manufacturing project in his company.
In 1980, the Indian government under Indira Gandhi opened PFY (polyester filament yarn) manufacturing to the private sector. Dhirubhai Ambani applied for a license to set up a PFY manufacturing plant. Obtaining the license was a long-drawn-out process requiring a strong connection within the bureaucracy system because the government, at the time, was restricting large-scale manufacturing, making the importation of yarn for the textiles impossible. In spite of stiff competition from Tatas, Birlas and 43 others, Dhirubhai was awarded the license, more commonly addressed as License Raj. To help him build the PFY plant, Dhirubhai pulled his eldest son out of Stanford, where he was studying for his MBA, to work with him in the company. Ambani did not return to his university program, leading Reliance's backward integration, where companies own their suppliers to generate more revenue and improve efficiency, in 1981 from textiles into polyester fibers and further into petrochemicals, which the yarns were made from. After joining the company, he reported daily to Rasikbhai Meswani, then executive director. The company was being built from scratch with the principle of everybody contributing to the business and not heavily depend on selected individuals. Dhirubhai treated him as a business partner allowing him the freedom to contribute even with little experience. This principle came into play after Rasikbhai's death in 1985 along with Dhirubhai suffering a stroke in 1986 when all the responsibility shifted to Ambani and his brother. Mukesh Ambani set up Reliance Infocomm Limited (now Reliance Communications Limited), which was focused on information and communications technology initiatives. At the age of 24, Ambani was given charge of the construction of Patalganga petrochemical plant when the company was heavily investing in oil refinery and petrochemicals.