In 1959, Harrison joined WMCA as the mid-day "Good Guy." Joe O'Brien (mornings) and Harrison gave WMCA a "one-two punch" for over eight years. Harrison told San Diego radio personality Gene Knight in an interview in 1994 that WMCA program director Ruth Meyer originally considered both Joe and Harry, separately, for the WMCA morning show.
Other WMCA "Good Guys" included Jack Spector, B. Mitchel Reed, Dan Daniel and Johnny Dark, and talk show host Barry Gray. Harrison became popular with his "Housewife Hall of Fame” feature, and participated in the 1966 WMCA Good Guy picnic. Often, he scored the highest ratings on WMCA. WABC program director Rick Sklar took note.
Every year, Harrison played seasonal songs, such as his holiday greeting "May You Always” in the winter (the Amy records single of this song made the Billboard Christmas charts in 1965), and Allan Sherman's summer camp novelty, "Hello Muddah, Hello Fadduh," throughout the summer months.
WABC personalities included, along with Harrison, Charlie Greer, Scott Muni, Bob Lewis, Lundy, Johnny Donovan, Dan Ingram, "Cousin Brucie" Bruce Morrow, Chuck Leonard, Bob Cruz, Frank Kingston Smith, and Roby Yonge, and others.
Harrison had a number of "trademark" phrases, such as "Every brand new day should be opened like a precious gift", "Stay well, stay happy, stay right here" and "Harry Harrison wishing you the best... because that's exactly what you deserve!” Also, on the last day of every year, Harrison would bring his four children to work with him and at the end of his shift, he would join them in giving listeners New Year's wishes.
Harrison was fired from WABC as the station changed direction in November, 1979.
On March 19, 2003, after a 44-year career in New York radio, Harrison left WCBS-FM, saying “I am not retiring.” His farewell to his loyal radio friends (from 5:30 to 10 am) was held before a packed, live audience at the Museum of Television and Radio in New York City. It offered old airchecks, and guest appearances by WCBS-FM colleagues Don K. Reed, Bobby Jay, Steve O'Brien, Randy Davis and Dan Taylor, his replacement, as well as his son and daughter, Patti. Harrison took phone calls from Bob Shannon, Mike Fitzgerald, Ed Baer and Ron Lundy. Songs included Gladys Knight's "Neither One of Us (Wants to Be the First to Say Goodbye)" and the Little River Band's "Reminiscing," before closing with "That's What Friends Are For."
Sadly, shortly after he left WCBS-FM, Harrison would lose his long-time wife, Patti, who he had always referred to as "Pretty Patti" on the air.
On Memorial Day, May 30, 2005, Harry and Cousin Bruce Morrow were guests on WABC Radio’s annual “Rewound” show. Four days later, on June 3, WCBS-FM ended its "oldies" format, in favor of the new “Jack” format. (Ironically, Harrison's voice was last heard on New York radio, not on WCBS-FM, but on WABC.)