He established the record production division for the company, working with producers, arrangers, musicians, and songs from writer/artists including Fleetwood Mac, Carole King, Melissa Manchester, and Cat Stevens.

He was transferred from New York to West Coast operations in the newly created position of division vice president, artist and repertoire.

He also worked on Whitney Houston's debut album in addition to projects involving acts such as Barry Manilow, Billy Ocean, the Thompson Twins, and Dionne Warwick.

In February 1985, Portnow was appointed vice president, artists and repertoire, for EMI America Records where he was responsible for all A&R activity worldwide.

He helped establish a black music department, played a role in the signing of superstar Robert Palmer, and brought platinum and gold album recording artists Pet Shop Boys and Najee to the company.

Throughout his career, Portnow has been involved in many soundtrack projects, including Ghostbusters, 9 To 5, The Stunt Man, The World's Greatest Lover, and the 1986 hit About Last Night.

During the 51st Annual Grammy Awards in 2009, Portnow spoke about the election of President Barack Obama and encouraged his administration to add a cabinet-level position for Secretary of the Arts.

[8] The campaign helped raise more than $12 million for the nonprofit organization, with the stated purpose of ensuring music people have a place to turn in times of financial, medical, and personal need.

[9] In May 2018, it was revealed that money intended for the Recording Academy charity MusiCares was siphoned off to pay for the cost overruns of hosting the 60th Annual Grammy Awards at New York City's Madison Square Garden.

[10] Concerning the controversies of hosting that year's Grammy Awards in New York, Dana Tomarken, the former executive vice president of the MusiCares foundation claimed wrongful termination.

She claimed that by having the MusiCares Person of the Year Tribute to Fleetwood Mac at Radio City Music Hall, the event had to forgo its traditional VIP dinner and silent auction.

[14] In November 2023, an unnamed woman filed a lawsuit against Portnow in Manhattan under New York's Adult Survivors Act, accusing him of sexual assault.

In October 2003, the City Of Hope presented Portnow with its top philanthropy honor, the Spirit of Life Award, at a gala event that raised more than $2.3 million to benefit research and treatment efforts.

Other honors include the George Washington University's Distinguished Alumni Achievement Award, and inclusion in Billboard magazine's Power 100 and the Variety500 industry lists.