Timmer was born in Hierden, Harderwijk, Gelderland. He spent his first 11 senior seasons in the second division, with FC Zwolle – named PEC in his first year. In 2000, he moved to AZ Alkmaar, making his Eredivisie debut at almost 29 and also serving unassuming loans at Feyenoord and AFC Ajax. He was part of the Feyenoord squad that won the 2001–02 UEFA Cup, and was an unused substitute in the final.