The verdict was read shortly after 5 p.m. Thursday.
Jeffrey Willis denied any role in Rebekah Bletsch's death in Muskegon County's Dalton Township, but the evidence against him was strong.
Willis now faces a mandatory sentence of life in prison with no chance for parole.
Two other cases still are pending. He's charged with trying to kidnap a teenager and killing a gas station clerk, Jessica Heeringa, whose body still hasn't been found.
A gun in Willis' van matched the weapon used in the Bletsch shooting. Willis tried to pin her death on a cousin when he testified Wednesday.
Defense attorney Fred Johnson said Willis isn't "likeable," but he urged jurors to set that aside.