Angelinos will stream into polling stations to cast their ballots and choose the next mayor of Los Angeles on Tuesday.
The candidates are now vying for the last undecided voters in what has become a tight race between Garcetti and Greuel. They both believe they are the best candidate to run Los Angeles.
Greuel and her supporters met at her field office in Boyle Heights around 5 a.m. before she cast her ballot at the Unitarian Universalist Church in Studio City.
Greuel's volunteers prepared to go door to door to gather supporters and urge them to get to the polls. She said she will be campaigning until the polls close.
"I won my first race by 225 votes out of 30,000, I know what it takes," Greuel said. "I've got a great team and a great group of volunteers."
If elected, Greuel would be the first female mayor of Los Angeles.
Garcetti and his wife cast their ballots in Atwater Village in the morning before heading out to gather up voters.
"Today I'm going to be going out and talking to voters all day long," Garcetti said. "Until 7:59 p.m., I'm going to be calling, showing up, going to subway stops, talking to people at stores and shopping areas, saying 'you got to go, it's not too late. You can still get there.'"
According to the Garcetti campaign, 3,000 volunteers are helping get voters to the pools the traditional way and through new media. Some of his volunteers woke up early and met at his field office in Cypress Park to take to the phones and travel door to door in a last minute attempt to get voters to the polls. Others used Twitter and Facebook to get the word out.
The latest exclusive Eyewitness News poll shows Garcetti leading Greuel 49 percent to 44 percent.
It appears Garcetti has the momentum in the race, but 7 percent of voters are still undecided.
The two Democrats are facing a possible historically low voter turnout but say they are confident Angelinos will vote and check the box next to their name. It's estimated that only 1 in 4 voters will turn out.
"I'm really energized. I certainly left everything out there on the field," Garcetti said. "We haven't left a single door unknocked. There's not a single call we didn't make."
"I feel very confident because we've been talking to voters every single day and we expect thousands of people to be out there today, knocking on doors and reminding people so this is a race to make sure you get your voters out," said Greuel.
This is a non-partisan race. Both candidates are Democrats and both have worked at City Hall for years.
Experts suggest the race is so close, a winner may not be announced Tuesday. It may take days to count the ballots.
The next mayor will lead the city through the budget crisis that could leave Los Angeles bankrupt and succeed Mayor Antonio Villaraigosa, who's leaving office July 1 after two terms.
Also on the ballot are the races for city attorney and controller, as well as four measures.
Former Assemblyman Mike Feuer will face incumbent Carmen Trutanich in the race for city attorney.
Longtime City Councilman Dennis Zine is running against attorney and businessman Ron Galperin for city controller.
Proposition D would limit the number of pot dispensaries at 135 and raise taxes slightly; Proposition E would cap the number at the same level but raise no new taxes; Proposition F wouldn't limit the number of pot shops but would put strict controls such as audits and background checks on employees, while also raising taxes.
Polls opened at 7 a.m. and will remain open until 8 p.m.
The Associated Press contributed to this report.