An all-clear was given after officials determined the symptoms didn't meet criteria for Ebola.
The woman told authorities that she and the child had traveled in the African country of Gabon, Deputy Clark County Fire Chief Jeff Buchanan said.
Neither she nor the boy, about a year old, was hospitalized, Buchanan said. Their names were not made public.
McCarran International Airport officials said Delta Flight 495 from John F. Kennedy Airport was parked on the tarmac about 11 a.m. while officials from the U.S. Centers for Disease Control and Prevention and the Southern Nevada Health District responded.
The quarantine was ordered after authorities were told that a passenger who had recently traveled to Africa had vomited on board, airport spokeswoman Christine Crews said.
A CDC official said later that Gabon is not one of the West African countries affected by the Ebola outbreak.
The Boeing 737-800 flight had 166 passengers and crew members aboard, airline spokesman Morgan Durrant said. The passenger became sick within the last 30 minutes of the nearly four-hour flight, Durrant said.
Ambulances and CCFD vehicles surrounded the plane after it landed. Paramedics donned protective gear to examine the woman and child, Buchanan said.
McCarran spokeswoman Christine Crews said the flight was quarantined at the gate "after reports that a passenger who had recently traveled in Africa vomited on board the aircraft."
"Clark County Fire Department, the Centers for Disease Control and the Southern Nevada Health District have responded. After a thorough assessment, it has been determined that the affected passenger does not meet the criteria for Ebola."
UMC spokeswoman D'Anita Cohen said the hospital was contacted by the airport about two unconfirmed cases of Ebola-like symptoms. She said UMC staffers originally prepared for two patients to be transported to the hospital, but that alert was cancelled when officials determined that symptoms did not meet the Ebola criteria.
A county spokesman confirmed that no patients were being transported to UMC.
McCarran sent out a Twitter message at 1:32 p.m. stating all passengers had deplaned and nobody had been quarantined or transported.
The incident came a day before body-temperature checks begin for passengers arriving at Kennedy International from three West African countries experiencing the Ebola outbreak: Guinea, Liberia and Sierra Leone.
Screenings are slated to begin next week at four other major airports: Newark Liberty, Washington's Dulles, Chicago's O'Hare and Hartsfield-Jackson Atlanta airport.
The CDC says early symptoms of Ebola include fever greater than 101.5 degrees Fahrenheit, severe headache, muscle and stomach pain, weakness, diarrhea, vomiting and unexplained bleeding or bruising. Symptoms may appear anywhere from two to 21 days after exposure to the virus, but the average is eight to 10 days.