Last year Tonmawr had to beat Seven Sisters to remain in the division, but now they are on their way into Division 1 West next season - the highest league ranking in their history.
Centre Lee Banfield crossed the Seven line twice and other tries came from scrum half Lee Gunnell and wing Darran Griffiths. Outside half Austin Howells added two conversions and penalty.
Having secured one title, Hill's men will now turn their attentions to winning the Worthington Silver Ball for the first time. They meet 2005 champions Penallta in the final at Sardis Road next week.
Penallta, who won the ASDA Division 3 East title this season, were beaten 17-7 at Newport HSOB.