He started out as a DJ for Jazzy Jay back in the late 1980s and was at the same time perfecting his skills in beat making and turntablism, and, together with rhyme partner Master Rob, he was one half of the group Ultimate Force. The group signed with Jazzy Jay's Strong City Records, and Diamond and Rob started recording their debut album, I'm Not Playin', in 1988 and released the 12-inch single with the same title, which spawned a buzz in the underground. The album was completed in 1990, but it got caught up in label politics, such as the shutdown of Strong City distributor Uni Records, and was shelved until 2007 when it was released through Traffic Entertainment. One of the last songs recorded for the album was a Diamond D solo song in which he actually picked up the mike for the first time. The song was called "The Best-Kept Secret." As Ultimate Force dissolved, record executives got their eyes on the Bronx phenomenon, which eventually resulted in the release of Diamond's debut album, Stunts, Blunts and Hip Hop (released under the moniker Diamond & the Psychotic Neurotics), in 1992. The album is considered to be one of the finest D.I.T.C. solo LPs and features early appearances from Big L and Fat Joe, the latter of whose 1993 debut album, Represent, was mainly produced by Diamond D