Dabbs was born into slavery, probably late in the 1840s, on the Charlotte County plantation of John Garnett. George Dabbs and Frankie Dabbs were his parents, but nothing else is known about his childhood, nor is it certain when or under what circumstances he became free. In Charlotte County on December 29, 1869, Dabbs married Sarah Ann Brown. Before her death on an unrecorded date after December 17, 1884, they had at least two sons.
In the census taken in August 1870 Dabbs was described as a twenty-one-year-old farm laborer who could neither read nor write. It is unclear how he first became involved in post–politics, but in October 1875 Radical Republicans in Charlotte County selected him as the party’s candidate for the House of Delegates in what the Charlotte Gazette described as a “somewhat excited and stormy discussion.” In the election the following month he received 1,283 votes while the incumbent and a third candidate tallied 630 and 261 ballots, respectively. As a member of the assembly that met in two sessions from December 1875 through March 1876 and then from December 1876 until April 1877, Dabbs served on the Committee on Labor and the Poor. He spoke little, but in January 1877 he introduced a bill to amend a sheep protection law in Charlotte, Clarke, and Frederick counties. Later that month, the resolution was dismissed.
At a meeting in October 1877 the county’s Radical Republicans, by one vote, rejected Dabbs in favor of another candidate to seek the House of Delegates seat. He continued to speak at county meetings, however, and to support party candidates. Dabbs aligned himself with the Readjuster faction of the Republican Party, which supported a partial repudiation of the state’s antebellum public debt. In November 1882 he dictated a letter to U.S. senatoraffirming his loyalty and service to the Readjusters, while requesting an appointment as a railway postal clerk for a young man in Charlotte County.
Dabbs canvassed Charlotte County in the weeks leading up to the November 1883 election. He stumped in nearly every precinct for the Readjuster candidate for the House of Delegates. Dabbs dictated another letter to Mahone in October informing him that the canvass was going well and predicting that party turnout at the polls would be substantial. Dabbs emphasized that he would continue his work until the election but informed Mahone that the candidate did not have the resources to pay him. He explained that his family required his support and they would suffer while he canvassed unless he could be paid from the campaign fund.
A civic leader in the black community, Dabbs served on the committee of arrangements in April 1896 for a gathering of African Americans discussing issues of citizenship as well as mental, moral, religious, and financial advancement. On March 30, 1898, he married twenty-one-year-old Sarah Catherine Howell in Charlotte County. No children are recorded from the marriage. Although he received little, if any, formal education, Dabbs may have learned to read and write by 1900, as reported by the census enumerator. By 1910 he and his wife had moved to Baltimore, where he worked as a brickyard laborer. Isaac Dabbs died on an unknown date after the census enumeration of his ward on April 27, 1910.