While attending Waseda University in Japan, Nobuyuki Idei first focused on photography, but at his father's urging he shifted his major to economics.Upon graduation in March 1960, he was hired at Sony, but he soon left the company to attend the London School of Economics. Because of his poor English skills, he struggled in his classes, but a professor took a liking to him and persuaded him to try the Geneva Graduate Institute where he eventually mastered both French and English. 

Sony rehired Idei to work in Switzerland, as the company was expanding its presence in Europe in the 1960s. Idei was sent to Paris to establish Sony France SA when he was only 31 years old; during this period he developed his ability to work with people from disparate cultures, and he established his talent for solving problems and creating new businesses. In 1972, as Sony's enterprises expanded in Europe, Idei was appointed manager of the Europe Section of the International Division of Sony, responsible for Sony's operations on that continent.

After 17 years in Europe, Idei was brought back to Japan in February 1979 to become the general manager of Sony's Audio Division. Sony executives believed that his marketing expertise, developed while creating new enterprises in Europe, would be put to good use in the marketing of a new Sony gadget, the Walkman. Idei also led the development of the audio CD player. 

In 1985 Idei worked on the introduction of another high-stakes gamble, the Sony eight-millimeter camcorder. This device made it easy to make home movies anywhere and was the ancestor of handheld videotape and videodisc recorders. In April 1988 Idei was made Senior General Manager of Sony's Home Video Group.

In June 1989 Idei was named to Sony's Board of Directors and Senior General Manager of Sony's Advertising and Marketing Communication Strategy Group in July 1990. He began promoting Sony's brand image at home and abroad, linking it with technological innovations and identifying it with high quality products. In June 1994 Idei advanced to Managing Director of Sony, ranking him 15th among Sony's top executives.

On 22 March 1995, Idei was introduced to the world as Sony's next President. Observers were surprised because he had been considered too far down the management ladder to be eligible for such a position in a company that valued seniority. In April he became president and COO of Sony Corporation.

For his role in changing how Sony did business, Idei was the first recipient of Fortune magazine's Asia's Man of the Year award in 1998. In May he added Co-chief Executive Officer to his titles. That March Sony grossed $56.3 billion and netted $4.3 billion for the fiscal year. Idei became CEO in 1999.

In 2006, Idei joined the board leading Accenture. On 28 September 2011, Idei joined the board of directors of Lenovo.
Idei founded his own consulting firm Quantum Leaps Corporation on his retirement from Sony. He was also on the board of companies including General Motors and Baidu.