Kansas City ran its winning streak to five games and handed Seattle its fourth setback in five outings.
The Royals jumped to an 8-0 lead through four innings, scoring twice on double-play grounders and once on a balk.
Teahen had a solo homer in the third and a two-run single in the fourth. Jacobs doubled home two runs in the first and brought home Teahen with a single in the ninth.
That outburst allowed Sidney Ponson to pick up his first win of the season. Ponson (1-4) allowed a run on eight hits over 7 1/3 innings.
Seattle's Ken Griffey Jr., who missed three games with stomach problems, had a double and a walk in his return.
Carlos Silva (1-3) took the loss, surrendering six runs on eight hits in three innings.