He was then admitted to the bar, and at different points served as counsel of the Brooklyn Excise Department and the Sheriff of Kings County.
He was appointed city magistrate in 1897, making him the first Brooklyn Jew to hold a judicial position.
[4] Brenner was active in the Republican Party, and was considered the leader of the Eighth Assembly District.
[7] Brenner died from heart disease while presiding at a meeting of the board of trustees of Congregation Beth Elohim.
Among those who attended the funeral were New York Supreme Court Justices Stephen Callaghan, Leander B. Faber, James Van Siclen, Lewis L. Fawcett, James C. Cropsey, and Charles H. Kelby, former Justice Luke Stapleton, former Chief Judge of the New York Court of Appeals Edgar M. Cullen, Republican-Coalition mayoral candidate Henry H. Curran, Surrogate George A. Wingate, Senator William M. Calder, Borough President Edward J. Riegelmann, Queens Republican leader Joseph H. DeBragga, Manhattan Republican leader Samuel S. Koenig, Brooklyn's Republican district leaders, Congregation Beth Elohim trustees (including District Attorney Harry E. Lewis, Meier Steinbrink, and Manasseh Miller), representations from the Federal Club the 8th Assembly District (Brenner's district) and the Congregation Beth Elohim Sunday School and women's auxiliary, and delegations from the Bedford Avenue Temple, the Unity Club, the Council of Jewish Women (which his daughter Rose was the national president of), and women political leaders from the various districts.