The union has 23,000 members in Oregon, with workers in the public and private sector, including truck drivers and warehouse workers.
Hass said the endorsement was personal for him.
It's also politically significant—in that one of his opponents in the Democratic primary, Sen. Shemia Fagan (D-East Portland) won the endorsement of the third largest public employee union over the weekend. The Teamsters endorsement means a split in support from labor.
Hass's depth of his experience—he has served in the state Senate since 2007—was at least part of what proved important to the Teamsters.
"Based on his long tenure and experience, he has the capacity to bring all sides together to find consensus among the very polarized legislative body, the electorate and the state," says Mark MacPherson, the political coordinator for the joint council.
Hass faces fellow state Sen. Shemia Fagan (D-East Portland), former state agency director Cameron Smith and Jamie McCleod-Skinner, an elected school board member, in the May Democratic primary.