But GOP hopes of flipping the seat were dashed early with NBC News and other media outlets calling the race about a half-hour after polls closed in the Rocky Mountain state.
With 68% of votes counted, Bennet led O'Dea, 55.9% to 41.7%.
Bennet, 57, a former chief of staff to his Senate colleague John Hickenlooper, is seen as a moderate, although he has championed marijuana reform and environmental issues.
In the Senate since 2009, Bennet ran for president in 2020, joining a crowded Democratic field that also included Hickenlooper, but he dropped out after the New Hampshire primary.
Bennet told supporters in Denver that he'll spend the next six years working to bring more economic opportunity to working-class Coloradans.
"As we stand here tonight, we have worst income inequality that we've had in a century in the United States of America," the soon-to-be three-term senator said.
"And I think that's unacceptable, I think that is unacceptable. We have to change that."
O’Dea was seen by many as an ideal Republican candidate — so much so that Democrats tried to stop him from winning the GOP nomination — but national polarization and Colorado’s leftward shift proved impossible for him to overcome.
O'Dea, a construction company CEO who had never run for office before, distanced himself from former President Donald Trump and campaigned as a commonsense conservative who supports abortion rights and same-sex marriage.
He said his philosophy was, “You live your life, I’ll live mine.”
After O’Dea defeated a Trump-aligned candidate in the Republican primary, Trump swiftly labeled O’Dea a “RINO” (Republican in Name Only) and said on his social media platform Truth Social: “MAGA doesn’t Vote for stupid people with big mouths. Good luck Joe!”
Notably, Florida Gov. Ron DeSantis, a potential rival to Trump for the 2024 presidential nomination, made a point of endorsing O’Dea, prompting criticism from Trump.
Colorado was a red state, then purple and now increasingly blue as it attracts well-educated transplants from places like California drawn to its natural beauty and strong economy.
Bennet's re-election should give Democrats cause for optimism as they look to hold the state in 2024.