Lafayette (19-14), the second seed, led 35-33 at intermission but opened the second half on a 17-7 run. Johnson, Hinrichs and Trist accounted for all but three points during the run.
Third-seeded Lehigh (21-9) got back to within 66-61 at the 5:35 mark but was outscored 16-8 the rest of the way.
The Mountain Hawks outshot Lafayette 46 percent (22 of 47) to 44 percent (24 of 54) but lost the rebounding battle 35-25. Lafayette turned 15 offensive boards into 17 second-chance points.
Mackey McNight led Lehigh with 22 points and Holden Greiner had 16.