[2][3] Martiniuk began his career at the municipal level, serving as a school trustee on the Waterloo County Board of Education, an alderman in Preston, and chair of the Waterloo Regional Police Commission.
[4] He was easily re-elected in the 1999 election, defeating Liberal Jerry Boyle by over 14,000 votes.
[8] In 2004, he supported John Tory's successful bid replace Ernie Eves as provincial PC leader.
In 2008 he supported Tim Hudak's successful PC leadership bid.
[8] He was a director of the St. John Ambulance, Cambridge United Way, Preston-Hespeler Rotary Club, Trinity Community Table, Preston YMCA, Chair, Conestoga College Advisory Committee on Criminology before entering provincial politics, and served as president of the Cambridge Chamber of Commerce.