Pearce handed Baltimore a 3-1 lead in the fifth and four Baltimore pitchers limited the Angels to five hits.
Miguel Gonzalez (1-0), making his first career start, gave up a run on three hits over seven innings with six strikeouts to get the win. He had made three relief appearances this year prior to getting the starting assignment.
The Angels closed within a run in the eighth on a two-out homer by Mike Trout and then put the next two batters on base. A popup by Kendrys Morales ended the threat.
Jim Johnson worked a 1-2-3 ninth for his 26th save.
Los Angeles has lost four of its last five contests and in that span has still gained a game on the first-place Texas Rangers in the American League West.
C.J. Wilson (9-5) suffered the setback, giving up the home run to Pearce in a seven-inning performance.