A spokesman for Cochran confirmed the senator's endorsement in a statement to The Hill.
Hagel has secured support from leading Senate Democrats and received very little opposition from that side of the aisle. However, top Senate Republicans have remained hesitant to back Hagel, citing his stance on the defense budget and alleged conflicts of interest.
Hagel met with senators earlier this month, ahead of his confirmation hearing before the Senate Armed Services Committee on Thursday. Top Senate Republicans signaled that they would wait until the confirmation hearing before passing judgement on Hagel. Democrats hold a 55-45 advantage in the Senate, so Hagel would need five Republican votes to reach the 60-vote threshold necessary to prevent a GOP filibuster.