Dimondstein began working for the United States Postal Service in Greensboro, North Carolina, in 1983.
[3] The following year, he was appointed as the union's National Lead Field Organizer.
For his successes in the private sector, he was in 2001 made the AFL-CIO Southern Organizer of the Year Award.
[1] In 2013, Dimondstein stood for the presidency of the union, defeating incumbent Cliff Guffey.
He focused on opposing potential privatization of the post office, and of reducing deliveries to five days a week, and proposed doing so by working more closely with other AFL-CIO affiliates.